JP3433075B2 - Method of manufacturing nitride semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a nitride-based semiconductor device that can be used in a semiconductor laser or a light emitting diode, and particularly has good ohmic contact with an electrode, low resistance, and low operating voltage. The present invention relates to a method for manufacturing a nitride semiconductor device .

[0002]

2. Description of the Related Art In recent years, Ga has been used as a material for a light emitting diode (hereinafter, also referred to as an LED) and a semiconductor laser (hereinafter, also referred to as an LD) in a short wavelength range from blue to ultraviolet.
Nitride-based semiconductors such as AlGaN are attracting attention as well as N. In particular, the InGaAlN mixed crystal is III-
It has the largest direct transition type energy gap in the V-group compound semiconductor mixed crystal, and is attracting attention as a light emitting device material in the 0.2 to 0.6 μm band, that is, in the red to violet region.

A semiconductor light emitting device using a nitride-based semiconductor material of this type requires a p-type conduction layer and an n-type conduction layer made of a nitride-based semiconductor as a current injection layer and a contact layer with an electrode.

When manufacturing a current injection type light emitting device, p
Since the n-junction type is basically used, control of the conductivity type and conductivity (acceptor concentration, carrier concentration) of the p-type conductive layer and the n-type conductive layer is essential. In the InAlGaN-based material, the conductivity type of the n-type conductive layer can be controlled relatively easily by using Si as an impurity.

On the other hand, it is difficult to control the conductivity type and the conductivity (acceptor concentration, carrier concentration) of the p-type conductive layer. To form this p-type conductive layer, magnesium (Mg) or zinc (Zn) is usually used as a dopant, and a hydrogen carrier gas (H ₂ ) and an ammonia gas (N
There is a system in which a growth substrate kept at a high temperature of about 1100 ° C. is installed in H ₃ ) and Ga raw material and Al raw material are supplied onto the growth substrate.

However, the Mg-doped nitride-based semiconductor layers such as the Mg-doped GaN layer and the AlGaN layer produced by this method show high resistance and do not show p-type conduction.

This is because, for example, the impurity levels of Zn and Mg are deep, and particularly in the case of growth by MOCVD, active hydrogen atoms decomposed from ammonia (NH ₃ ) as a source gas or hydrogen as a carrier gas or The presence of other residual impurities may prevent activation of Mg and Zn to acceptors (JAVan Vechtenet
al., Jpn.J.Appl.Phys.31 (1992) 3662).

The Mg-doped InAlGaN layer is MOCVD
In the case of growing by the method, during the growth of the Mg doped layer or after the growth, the substrate temperature is lowered to room temperature, and NH ₃ and hydrogen from the carrier gas are taken into the crystal together with Mg,
H ⁺ inactivates the acceptor, resulting in a high resistance layer. For example, Mg is 1 × 10 ²⁰ cm ^-3
When GaN is doped at a concentration of 1, the hydrogen concentration is also 1 × 1
It is taken in as much as about 0 ²⁰ cm ^-3 . This Mg-doped GaN layer has a hydrogen concentration 10 times or more that of an undoped or Si-doped GaN layer grown under the same conditions, and as-gross is determined by Hall measurement or CV measurement.
It has been confirmed that wn has high resistance.

[0009] Electron beam irradiation (H. Amano et a
L., Jpn.J.Appl.Phys.28 (1989) L2112) and heat treatment (S.Naka
mura et al., Jpn.J.Appl.Phys.31 (1992) 1258),
It was found that the activation rate of Mg is improved, and high brightness LE
Practical application of D and realization of LD oscillation have been made (S. Nakamu
ra et al., Jpn.J.Appl.Phys.35, (1996) L74.).

Therefore, in general, the Mg-doped nitride-based semiconductor layer is subjected to a post-process such as a heat treatment for desorbing hydrogen in a nitrogen gas atmosphere at about 600 ° C. to 800 ° C. after its formation.

After such a heat treatment step, the Mg-doped nitride semiconductor layer shows p-type conduction due to activation of Mg, but a high resistance layer is formed on the outermost surface of the growth layer. The reason why the high resistance layer is formed on the outermost surface of the growth layer will be described in detail below.

FIG. 37 is a schematic view showing the structure of a typical blue semiconductor laser using a nitride semiconductor. This blue semiconductor laser has a buffer layer (not shown), a GaN base layer 2, a GaN contact layer 3, and an n-type A on a sapphire substrate 1 by a metal organic chemical vapor deposition (MOCVD) method.
An lGaN current injection layer 4, an active layer 5 having a multiple quantum well (MQW) structure using InGaN, a p-type AlGaN current injection layer 6, and a p-type GaN contact layer 7 for forming a p-type electrode were sequentially formed. It has a multilayer structure.

During the formation of this type of multilayer structure, generally,
Hydrogen is used as a carrier gas except for the InGaN-based active layer 5. On the other hand, when forming the InGaN active layer 5, nitrogen is used as a carrier gas. In this multilayer structure, the p-type AlGaN current injection layer 6 and p
When forming the type GaN contact layer 7, Mg is used as a p-type dopant. Since Mg is not activated during growth, the multilayer structure is heat-treated in a nitrogen atmosphere after its formation.

After this heat treatment, a part of the multilayer structure is removed to a depth reaching the GaN contact layer 3 by the dry etching method, and then the n-side electrode 8 is formed on the GaN contact layer 3. Further, the p-side electrode 9 is formed on the p-type GaN contact layer 7 that has not been removed.
The sample having the electrodes 8 and 9 thus formed is cleaved to form a cavity end facet, and a blue semiconductor laser is manufactured.

However, this blue semiconductor laser is
Since the p-type GaN contact layer 7 has the high resistance portion on the outermost surface, the operating voltage is high, and it is difficult to inject a current necessary for laser oscillation into the device. Further, if an attempt is made to inject a current required for laser oscillation, the operating voltage rises to 20 V or higher, and the vicinity of the p-side electrode 9 is destroyed. In order to solve such a problem, it is essential to reduce the contact resistance of the p-side electrode 9.

Next, regarding this blue semiconductor laser, the concentration distribution of Mg, carbon, hydrogen, and oxygen in the depth direction before and after heat treatment in a nitrogen atmosphere was measured by secondary ion mass spectrometry (hereinafter, SIM).
S)). As a result, as shown in FIG. 38, the concentration of Mg is constant in the depth direction before and after the heat treatment. On the other hand, carbon (C), hydrogen (H), and oxygen (O) show a substantially constant concentration distribution along the depth direction of the sample before the heat treatment, but after the heat treatment, on the outermost surface of the growth layer of the sample, It is detected in a larger amount than in the growth layer. For example, when it is remarkable, carbon and hydrogen may be detected on the outermost surface of the growth layer by 1 to 2 orders of magnitude more than inside the growth layer.

Therefore, the reason why the contact resistance between the p-type GaN contact layer 7 and the p-side electrode 9 is high and the device voltage is high is that hydrogen is diffused from the inside of the growth layer to the surface by heat treatment and a large amount of hydrogen is present on the outermost surface. It can be mentioned that the residual causes the Mg to be inactivated by binding with Mg on the surface. Further, a large amount of carbon is present on the outermost surface of the growth layer due to diffusion from the inside of the growth layer or surface contaminants generated during heat treatment. In addition, oxygen is a surface oxide film generated during heat treatment,
Or, it is considered to be due to diffusion from the inside of the growth layer.

When the outermost surface of the growth layer is rich in oxygen and carbon, there are problems as shown in the following (1) to (3).
(1) There is a problem that the activation rate of a dopant such as Mg is lowered and the carrier density is lowered. (2) There is a problem that good ohmic contact with the electrode cannot be obtained. These (1) and (2) increase the contact resistance with the p-side electrode 9, increase the operating voltage of the element, shorten the element life, and reduce reliability. Further, (3) there is a problem that impurities are diffused through crystal defects such as threading dislocations and stacking faults, and leak current is increased.

Although such a nitride-based semiconductor device requires heat treatment, Mg in the growth layer is sufficiently activated due to differences in device structure such as the thickness of the p-type layer and the composition of each layer. Although the heat treatment time required for the heat treatment is different and the heat treatment time can be estimated to some extent by calculation considering the diffusion of hydrogen, it is not easy to determine the optimum value of the heat treatment time at the heat treatment temperature.

That is, although heat treatment is required, the optimum heat treatment temperature and time for dissociating hydrogen are unclear, so that hydrogen remains in the p-type conductive layers 6 and 7, or excessive heat treatment is performed. Therefore, it is highly possible that the activation rate of Mg is reduced. Further, the hydrogen remaining inside as described above causes the resistance of the entire device to be high, and causes the operating voltage of the device to rise in the same manner as the contact resistance.

From the viewpoint of solving such a problem, an attempt to obtain the p-type conductive layers 6 and 7 without using a heat treatment process is disclosed in Japanese Patent Application Laid-Open No. 8-125222. This publication describes a method of obtaining the p-type conductive layers 6 and 7 by replacing the atmosphere gas with an inert gas other than hydrogen gas and ammonia gas in the temperature decreasing process after the growth is completed. However, this method does not require a heat treatment step, but as described above, since a high resistance layer is formed in the growth layer due to the presence of residual hydrogen, good ohmic contact cannot be obtained, and device characteristics Not expected to improve. The publication also shows an example of growth in a nitrogen atmosphere, but it is shown that the Mg-doped layer obtained by this method is an insulator having a resistivity of 10 ⁸ Ωcm or more.

[0022]

As described above, the nitride semiconductor device and the method for manufacturing the same require special treatments such as heat treatment and electron beam irradiation after growth in order to activate Mg. It takes time, reduces productivity,
In addition to the problem of high cost, there is a problem of yield reduction and deterioration of crystal quality due to an increase in processing steps.

Further, due to the heat treatment after the growth, a large amount of hydrogen, carbon and oxygen are present on the surface of the growth layer, resulting in the p-type Ga.
There is a problem that the contact resistance of the N contact layer 7 is increased and the operating voltage of the device is increased. Further, there is a problem that the operating life of the LED does not reach the practical level and the reliability is lowered due to the deterioration in the vicinity of the p-side electrode 9.

Further, in the case of LD, if the contact resistance with the p-side electrode 9 is high, laser oscillation becomes difficult, or LE
Similar to D, there is a problem that the operating life is extremely short due to deterioration in the vicinity of the p-side electrode 9.

The present invention has been made in consideration of the above-mentioned circumstances, and the quality of the p-type conductive layer can be improved while reducing the cost and improving the productivity by eliminating the need for special treatments such as heat treatment and electron beam irradiation after the growth. Therefore, it is an object of the present invention to provide a method for manufacturing a nitride-based semiconductor device, which can improve the reliability of the device and thus improve the reliability.

Further, an object of the present invention can easily control the conductivity type of p-type conductive layer, having a good ohmic contact with low resistance, the nitride-based semiconductor device operating at a low operating voltage
It is to provide a manufacturing method of.

[0027]

(Structure) In order to solve the above problems, the present invention adopts the following structure.

[0028]

[0029]

[0030]

That is, according to the present invention (claim 1 ),
A step of forming a compound semiconductor layer having at least n-type conductivity and containing nitrogen as a constituent element, and a step of forming a compound semiconductor layer having p-type conductivity and containing nitrogen as a constituent element, by metalorganic vapor phase epitaxy. In the method of manufacturing a nitride-based semiconductor device containing, in the step of forming the compound semiconductor layer having p-type conductivity and containing nitrogen as a constituent element, at least the p-type dopant raw material and ammonia ( NH ₃ ) -containing source gas and CO, C
The use of O ₂ concentration 0.1 to 10 vol ppb range carrier gas of purified non <br/> active gas, characterized.

[0032]

Here, the step of forming a compound semiconductor layer having p-type conductivity and containing nitrogen as a constituent element is performed by using a group V source material.
The supply amount (mol) ratio (V / III ratio) of the group III raw material is
3000 or less for aN, 360 for GaAlN
It is desirable that the condition is 0 or less, and in the case of InGaN, the condition is 30,000 or less .

Further, after the step of forming a compound semiconductor layer having p-type conductivity and containing nitrogen as a constituent element as the outermost surface layer of the multilayer structure for devices and forming the outermost surface layer having p-type conduction, Stop the supply of organometallic raw materials for the membrane,
The p-type dopant raw material and substantially inert carrier gas given time, or supplied at a predetermined temperature, or subjected in the cooling process
It is desirable to pay .

[0035]

The p-type dopant material is preferably an organic magnesium (Mg) compound.

The predetermined time is 30 seconds or more and less than 1 hour, the predetermined temperature is 300 ° C. or higher and the growth temperature or lower, and the temperature lowering process is a natural temperature decrease within the predetermined time and the predetermined temperature range. And it is desirable to decrease the slope temperature.

[0038]

The present invention (Claim 4 ) is characterized in that
Manufacture of a nitride-based semiconductor device having a laminated structure of a compound semiconductor layer having at least n-type conductivity and containing nitrogen as a constituent element, a compound semiconductor layer having p-type conductivity and containing nitrogen as a constituent element, and an electrode In the method, at least a p-type dopant raw material, a raw material gas containing ammonia (NH ₃ ), and a carrier gas are used, and a compound semiconductor layer containing p-type impurity-added nitrogen as a constituent element is used as an outermost surface layer of a device multilayer structure. After the step of forming and forming the outermost surface layer to which the p-type impurity is added, the supply of the organometallic raw material for film formation is stopped, and the p-type dopant raw material and the carrier gas are supplied for a predetermined time at a predetermined temperature. Or during the cooling process
It is characterized by supplying .

[0040]

Here, the p-type dopant material is preferably an organic magnesium (Mg) compound.

[0042]

The predetermined time is 30 seconds or more and less than 1 hour, the predetermined temperature is 300 ° C. or higher and the growth temperature or lower, and the temperature lowering process is the natural temperature decrease within the predetermined time and the predetermined temperature range. And it is desirable to decrease the slope temperature.

[0044]

[0045]

[0046]

[0047]

(Operation) According to the present invention, In _x Al _y G
a _z B _1-xyz N _m P _n As _1-mn and other p-type compound semiconductor layers have a maximum oxygen concentration in the vicinity of the surface that is 5 times or less than the average in-plane oxygen concentration. To do. Further, it is preferably 3 times or less, more preferably 2 times or less. As a result, there is no region with high oxygen concentration locally in the wafer surface, so non-uniform injection (current), generation of non-emission region, influence on waveguiding, etc.
It is possible to eliminate adverse effects on resistance, electromigration, distortion, thermal characteristics, etc., and further improve reliability.

Further, In _x Al _y Ga _z B _1-xyz N _m
The maximum carbon concentration in the vicinity of the surface of a p-type compound semiconductor layer such as P _n As _1-mn is characterized by being 5 times or less the average value of the in-plane carbon concentration. Further, as in the above, it is preferably 3 times or less, more preferably 2 times or less. As a result, since there is no locally high carbon concentration region in the wafer surface, it is possible to eliminate adverse effects such as non-uniform implantation (current) and generation of non-light emitting region, and improve reliability, as described above. You can

In addition, the CO and CO ₂ concentrations in the carrier gas and the H ₂ concentration in the growth of the p-type compound semiconductor layer, and the raw material supply ratio (V / III) are regulated, so that The p-type additive impurities are activated without a heat treatment step, and a p-type electrically conductive layer having a high acceptor concentration and carrier concentration is obtained, and the initial characteristics, reliability, productivity, and cost of the device are significantly improved. Furthermore, since the contact resistance with the p-side electrode is reduced, the operating voltage of the element can be reduced, and the initial characteristics, yield, and reliability of the element are significantly improved.

[0051]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
3 is a cross-sectional view showing the structure of the semiconductor laser according to the embodiment of FIG. This semiconductor laser is provided on a sapphire substrate 11,
An undoped GaN base layer 12, an n-type GaN contact layer 13, an n-type AlGaN current injection layer 14, a GaN light guide layer 15, an InGaN active layer 16, a GaN light guide layer 17, and a p-type AlGaN current injection via a buffer layer (not shown). The layer 18 and the p-type GaN contact layer 19 have a multilayer structure in which they are sequentially formed.

A part of this multilayer structure extends from the outermost surface of the p-type GaN contact layer 19 to the n-type GaN contact layer 1.
The n-side electrode 20 is formed on the GaN contact layer 13 exposed by the dry etching method up to the depth reaching 3.

However, a small amount of hydrogen gas is used in addition to nitrogen which is the main carrier gas. In order to prevent alteration of the InGaN-based active layer, it is desirable to carry out low temperature growth after the growth of the active layer.
This is because it has the effect of increasing the growth rate, the effect of improving the flatness of the growth layer surface, and the effect of increasing the decomposition efficiency of the organic Mg raw material and increasing the incorporation of Mg into the growth layer.

On the p-type GaN contact layer 19 which is not removed in the multilayer structure, SiO for current confinement is formed.
_{The two} layers 21 are selectively formed, and the p-side electrode 22 is formed on the SiO ₂ layer 21 and the p-type GaN contact layer 19.

The semiconductor laser according to the present embodiment thus has the n-side electrode and the p-side electrode in the multilayer structure.

Although the details will be described later, p-type AlGaN
During formation of the current injection layer 18 and the p-type GaN contact layer 19 and during the temperature lowering process after formation, nitrogen is used as a carrier gas from the viewpoint of preventing the formation of the Mg-hydrogen complex and activating Mg. It is used. Hydrogen is used as the carrier gas for the organic raw material containing the p-type dopant from the viewpoint of improving the decomposition efficiency of the organic raw material.

Next, the manufacturing method and operation of the above semiconductor laser will be described.

This semiconductor laser is manufactured by the well-known MOCVD method. Specifically, for example, as an organic metal raw material, trimethylgallium (TMG), trimethylaluminum (TMA), trimethylindium (TM)
I), biscyclopentadienyl magnesium (Cp ₂
Mg) is used. Ammonia (NH ₃ ) and silane (SiH ₄ ) are used as gas raw materials. Hydrogen and nitrogen are used as carrier gases.

First, the sapphire substrate 11 is subjected to organic cleaning and acid cleaning, and then placed on the susceptor which is heated by high frequency in the reaction chamber of the MOCVD apparatus. Next, the sapphire substrate 11 is subjected to vapor phase etching at a temperature of 1200 ° C. for about 10 minutes in an atmosphere in which hydrogen is introduced at a flow rate of 25 L / min under normal pressure, and the native oxide film on the surface is removed.

Then, 550 is formed on the sapphire substrate 11.
After the buffer layer is formed at a low temperature of about 0 ° C, the substrate temperature is 1100 ° C, hydrogen as a carrier gas is flowed at 20.5 L / min, ammonia is 9.5 L / min, and TMG is 100%.
The undoped GaN underlayer 12 is formed on the buffer layer by being supplied at a flow rate of cc / min for 60 minutes.

Further, SiH ₄ is flown at a flow rate of 10 cc / min to form the n-type GaN contact layer 13, and then TMA is flown at 60 cc / min, whereby the n-type AlGaN current injection layer 14 is formed. Is formed.
Here, the supply of SiH ₄ and TMA is stopped, and GaN
The light guide layer 15 is the undoped GaN base layer 1 described above.
It is formed under the same growth conditions as 2.

Thereafter, the substrate temperature is lowered to 780 ° C., the carrier gas is switched to 20.5 L / min of nitrogen, 9.5 L / min of ammonia, 9 cc / min of TMG,
The InGaN active layer 16 is formed by introducing TMI at a flow rate of 465 cc / min for about 30 minutes.

After the InGaN active layer 16 was formed, the substrate temperature was raised again to 1100 ° C., and when it reached 1100 ° C., the carrier gas was switched again to hydrogen 20.5 / min, and the GaN optical guide layer 17 was changed to It is formed under the same growth conditions as the GaN light guide layer 15.

The GaN light guide layer 17 may use nitrogen as a carrier gas. In this case, the effect of suppressing evaporation caused by exposing the InGaN layer 16 which is the active layer to high temperature hydrogen can be expected together.

By changing the carrier gas in the subsequent growth process and temperature lowering process as follows, three types of nitride-based blue semiconductor lasers of the specific example according to the present invention and the comparative examples 1 and 2 related to the prior art were prepared. Then, the characteristics were compared.

Specific Example A p-type conductive layer was formed according to the present invention. That is, it was prepared as follows by using nitrogen as a carrier gas in the growth process of the p-type conductive layer and the subsequent temperature lowering process.

After forming the GaN optical guide layer 17, the carrier gas is switched to nitrogen 20.5 L / min, ammonia 9.5 L / min, TMG 100 cc / min, and TMA 60.
cc / min, and Cp ₂ Mg of p-type dopant raw material is 25
cc / min, and 0.2 on the GaN light guide layer 17.
A 5 μm thick p-type AlGaN current injection layer 18 is formed. Also, Cp ₂ Mg was increased to 50 cc / min, and
A p-type GaN contact layer 19 having a thickness of 7 μm is formed.

However, a small amount of hydrogen gas may be used in addition to nitrogen as the main carrier gas. In order to prevent the deterioration of the InGaN-based active layer, it is desirable to carry out low temperature growth after the growth of the active layer.
This is because it has the effect of increasing the growth rate, the effect of improving the flatness of the growth layer surface, and the effect of increasing the decomposition efficiency of the organic Mg raw material and increasing the incorporation of Mg into the growth layer. The concentration of hydrogen introduced into the reaction tube can be appropriately selected, but is preferably 7% by volume or less, and more preferably 2% by volume or less.

Further, in the growth process of the p-type conductive layer, the ratio of ammonia gas (NH ₃ ) to nitrogen used as the main carrier gas is preferably around 0.5, and preferably in the range of 0.1-10. . When this ratio is low, island-like growth occurs and good morphology cannot be obtained, and when it is high, problems such as poor crystallinity occur.

After the growth of the p-type GaN contact layer 19, the supply of the organometallic raw material is stopped and the nitrogen carrier gas 20.5
/ Min, and only 9.5 L / min of ammonia were continuously supplied, and the substrate temperature was naturally lowered. However, the supply of ammonia is stopped when the substrate temperature reaches 350 ° C.

[Comparative Example 1] A method similar to the conventional method is used. That is, hydrogen is used as the main carrier gas in the growth process of the p-type conductive layer under the growth conditions of the above-described embodiment of the present invention and in the subsequent temperature decrease process.

Comparative Example 2 Hydrogen was used as the main carrier gas in the growth process of the p-type conductive layer under the growth conditions of the above-described specific example of the present invention. In the cooling process after growth, nitrogen is used as the main carrier gas as in the specific example of the present invention.

(Evaluation) (CV measurement) These, specific examples, comparative examples 1 and 2
The CV measurement was performed on the three types of samples to measure the acceptor concentration of the p-type conductive layer.

As a result, for the sample of the specific example, a p-type conductive layer was obtained without heat treatment. P-type Al in the sample of this example
The GaN current injection layer 18 has an acceptor concentration of 6 × 10 ¹⁸ c
m ⁻³ , and the p-type GaN contact layer 19 has an acceptor concentration of 9 × 10 ¹⁸ cm ⁻³ . That is, in the sample of the specific example, both p-type conductive layers 18 and 19 were activated by Mg as an acceptor.

On the other hand, the samples of Comparative Example 1 and Comparative Example 2 had high resistance without heat treatment and did not become p-type. next,
The samples of Comparative Example 1 and Comparative Example 2 were subjected to 7 in a nitrogen atmosphere.
After heat treatment at 50 ° C. for 30 minutes, the same CV measurement was performed. The p-type AlGaN current injection layer 18 had an acceptor concentration of 4 × 10 ¹⁸ cm ⁻³ , and the p-type GaN contact layer 19 had an acceptor concentration. Was 4 × 10 ¹⁸ cm ^−3, and Mg was activated as an acceptor.

(IV measurement) On the other hand, an n-type electrode 20 and a p-type electrode 22 were formed on these three types of samples in the same manner as described above to prepare a sample with electrodes having the structure shown in FIG.

Good ohmic contact was obtained from the sample with electrode of the specific example.

On the other hand, the samples with electrodes of Comparative Example 1 and Comparative Example 2 were all poor in ohmic contact.

(Laser oscillation characteristic) Next, a semiconductor laser was prepared from these three types of electrode-attached samples, and the characteristic was evaluated.

That is, these three types of electrode-attached samples (wafers) were cleaved to a size of 350 μm to form a resonator mirror, and three types of semiconductor lasers were produced.

The semiconductor laser of the specific example has an operating voltage of 5V,
At a threshold current density of 5 kA / cm ² , a wavelength of 420
A room temperature continuous wave of nm was obtained.

On the other hand, in the semiconductor lasers of Comparative Example 1 and Comparative Example 2, the operating voltage increased to 35 V, laser oscillation did not occur,
The element was destroyed due to deterioration in the vicinity of the p-side electrode.

(Impurity Concentration Distribution in the Depth Direction) Next, before and after the heat treatment between these three types of samples, the magnesium (M
g), hydrogen (H), carbon (C), oxygen (O) concentration distributions were examined.

In the sample of the specific example, as shown in FIG. 2A, the Mg concentration was constant at about 5 × 10 ¹⁹ cm ⁻³ along the depth direction. In addition, the hydrogen concentration of the sample of the specific example is the lower limit of detection (2 × 10 ¹⁸ cm ⁻³ ) or less, and hydrogen is not detected even on the outermost surface of the growth layer. The carbon concentration of the sample of the specific example was constant at about 2 × 10 ¹⁷ cm ⁻³ in the growth layer.
Moreover, the oxygen concentration of the sample of the specific example is lower than the detection lower limit (1 × 10 5
It was less than ¹⁷ cm ^-3 ).

On the other hand, Comparative Example 1 and Comparative Example 2 are shown in FIG.
As shown in (b), the Mg concentration was about 5 × 10 ¹⁹ c regardless of before and after the heat treatment, similar to the sample of the specific example.
It was m ^-3 .

In Comparative Examples 1 and 2, the hydrogen concentration was about 4 × 10 ¹⁹ cm ^-3 before the heat treatment. Further, in Comparative Examples 1 and 2, the hydrogen concentration after the heat treatment was below the detection limit (2 × 10 ¹⁸ cm ⁻³ ) inside the multilayer growth film, but about 3 × 10 ¹⁹ at the outermost surface of the growth layer. It became cm ^-3 . Further, in Comparative Examples 1 and 2, hydrogen was detected at about 3 × 10 ¹⁹ cm ^{−3 on the} outermost surface of the growth layer even if the heat treatment was further applied for 30 minutes.

Further, in Comparative Examples 1 and 2, the carbon concentration was constant at about 3 × 10 ¹⁷ cm ^-3 in the growth layer before the heat treatment. Further, in Comparative Examples 1 and 2, after the heat treatment, the carbon concentration was increased to about 8 × 10 ¹⁹ cm ^{−3 on the} growth layer surface. In Comparative Examples 1 and 2, the oxygen concentration before the heat treatment was below the lower limit of detection (1 × 10 ¹⁷ cm ⁻³ ), but after the heat treatment, about 7 × 10 ¹⁸ cm ^{−3 was} detected near the surface. It was The oxygen concentration after this heat treatment is about 7 × 10 ¹⁸
cm ^-3 is an extraction of the lowest measurement result, and usually shows a value higher by about one digit or more.

(In-Plane Impurity Concentration Distribution) Next, with respect to the sample of the specific example and the sample of Comparative Example 1, the in-plane distribution of the impurity concentration near the surface of the p-type contact layer was examined by SIMS analysis. The samples of the specific example and the comparative example 1 were examined for carbon (C), oxygen (O), hydrogen (H), and silicon (Si). These results are shown in FIGS. Incidentally, these figures correspond to the in-plane distribution of the impurity concentration, and the count number of each impurity cluster in the plane is based on the correspondence table between the count number and the shade on the right side of the figure,
Indicated by mapping.

As shown in FIG. 3, FIG. 4, FIG. 5 and FIG. 6, the sample of the specific example has a substantially in-plane distribution of carbon concentration, oxygen concentration, hydrogen concentration and silicon concentration at a position deeper than 100 nm from the surface. It is uniform and there is no locally high part for any impurities. That is, in the sample of the specific example, the maximum concentration of each impurity was 5 times or less than the average concentration of the same impurity in the plane.

Next, the results of the sample of Comparative Example 1 will be described after describing the method of displaying the drawings. 7, FIG. 8, FIG. 9 and FIG. 10 are the same as FIG. 3 described above and the like, and the count numbers of the clusters of each impurity are shown by dividing them into shades.

Here, the samples of Comparative Example 1 are shown in FIGS.
As shown in FIGS. 9 and 10, regarding the in-plane distribution of carbon concentration, oxygen concentration, hydrogen concentration, and silicon concentration, there are locally high portions in the plane.

That is, the value of the impurity concentration in Comparative Example 1 is higher by about one digit in the high concentration portion than in the average concentration portion. In particular, for the carbon concentration, the value of the high concentration part is 3 ×
10 ¹⁹ cm ^-3 , and the value of the average density part is 2 × 1
It was 0 ¹⁷ cm ^-3 . That is, in Comparative Example 1, the high carbon concentration is about two orders of magnitude higher than the average carbon concentration.

Further, in Comparative Example 1, as shown in FIGS. 7 and 8, locally high carbon and oxygen concentrations (not shown) are present even at a depth of 1 μm from the outermost surface.
On the other hand, the sample of the specific example does not have such locally high carbon concentration and oxygen concentration. In addition, in the sample of the specific example, a portion where the carbon concentration and the oxygen concentration are locally high as described above is generated by performing the annealing treatment.

In Comparative Example 1, due to the presence of locally high carbon and oxygen concentrations, the generation of non-uniform injection (current) non-emission regions, the influence on the waveguiding, the resistance,
Electromigration, distortion, thermal properties, etc. are adversely affected, reducing the reliability of the device. The specific example according to the present invention does not have such a problem.

Further, although not particularly mentioned, the hydrogen concentration and the silicon concentration also have locally high portions in Comparative Example 1, but do not have locally high portions in the specific example.

(Change in characteristics due to carrier gas) Next,
In the present invention, the difference in characteristics due to the use of nitrogen gas as the main carrier gas was examined using a specific example according to the present invention and a conventional comparative example 1. The results are shown in FIGS.
Shown in. In addition, "nitorogen carrier gas" in each figure shows a specific example, and "hidrogen carrier gas" shows Comparative Example 1.

FIG. 11 is a diagram showing the in-plane distribution of the growth rate (film thickness) in the GaN layer, which corresponds to the in-plane distribution of the film thickness. In the figure, the vertical axis represents the growth rate corresponding to the film thickness. The growth rate is a value obtained by dividing the film thickness by the growth time. The film thickness was measured by a well-known scanning electron microscope (SEM). The horizontal axis indicates a predetermined position on the upstream side of the gas in the wafer as "front" and a predetermined position on the downstream side as "back". The position of the center of the wafer is shown as "center". As shown in the drawing, the film thickness distribution of the specific example is substantially uniform within the wafer surface. On the other hand, the film thickness distribution of the comparative example is non-uniform in a V shape between “front” and “back”.

FIG. 12 is a graph showing the growth temperature dependence of the growth rate (film thickness) in the GaN layer, which corresponds to the growth temperature dependence of the film thickness. The vertical axis represents the growth rate (film thickness / growth time) at the center of the GaN layer. A well-known SEM was used for film thickness measurement. The horizontal axis shows the growth temperature. As shown, in the specific example, the film thickness of the GaN layer is substantially constant at the growth temperature of 1000 ° C to 1100 ° C. On the other hand, Comparative Example 1
The film thickness decreases as the growth temperature rises from 1050 ° C to 1120 ° C.

FIG. 13 is a diagram showing the growth temperature dependence of the acceptor concentration (p-type carrier density) in the p-type conductive layers 18 and 19. The acceptor concentration was measured by the well-known CV method. As shown, a specific example is 1000 ° C
The acceptor concentration is almost constant at the growth temperature of 1100 ° C. On the other hand, in Comparative Example 1, the acceptor concentration increases as the growth temperature rises from 1050 ° C to 1150 ° C.

FIG. 14 is a diagram showing the in-plane distribution of the Al composition in the GaAlN layer used for the current injection (cladding) layer. The vertical axis shows the Al composition, and the horizontal axis is the same as in FIG. The Al composition was measured by the well-known X-ray diffraction. As shown in the figure, the variation in the Al composition of the specific example is smaller than the variation in the Al composition of the comparative example 1.

From the above experimental results, in Comparative Example 1 and Comparative Example 2 in which a thin film layer to be a p-type conductive layer is grown in a hydrogen carrier gas and is made into p-type by a heat treatment after growth, the outermost surface of the multilayer structure, that is, In the case of a light emitting device, an increase in the concentration of hydrogen, carbon and oxygen presumed to be caused by heat treatment is observed on the outermost surface of the p-type contact layer, and the presence of this hydrogen deactivates Mg existing on the outermost surface. At the same time, the resistance is increased by carbon and oxygen existing on the outermost surface, and it is considered that ohmic contact with the p-side electrode cannot be obtained.

On the other hand, in the sample of the specific example according to the present invention,
Since the carrier gas in the growth process is substantially nitrogen gas, it is difficult for hydrogen to bond to Mg, and Mg can be activated without heat treatment. It is possible to eliminate the uneven distribution of hydrogen, carbon, oxygen and the like, and to prevent the inactivation of Mg by hydrogen and the high resistance of the surface by carbon and oxygen.

That is, according to the present embodiment, the heat treatment after the growth is unnecessary, the cost is reduced and the productivity is improved, and p
By improving the quality of the mold conduction layer, the operating voltage of the device can be greatly reduced even in semiconductor lasers that require higher current injection compared to light emitting diodes, laser oscillation is facilitated, the device life is greatly extended, and reliability is improved. Can be improved.

Further, according to the present embodiment, unlike Comparative Example 1 of the conventional method, there is no region where the carbon concentration or oxygen concentration is locally high, so that non-uniform current injection and non-emission region generation are generated. The influence on the waveguide, the resistance, the electromigration, the distortion, and the bad influence on the thermal characteristics can be eliminated, and the reliability can be further improved.

Further, according to this embodiment, since nitrogen gas is used as the main carrier gas and a small amount of hydrogen gas is contained as the other carrier gas, Mg in the semiconductor layer is
With respect to, the activation of nitrogen gas is promoted, and with regard to Mg in the source gas, hydrogen gas promotes decomposition of the source gas to facilitate mixing of Mg into the semiconductor layer. It is possible to improve.

Further, according to the present embodiment, the flow rate of nitrogen gas is in the range of 5 times to 2000 times the flow rate of hydrogen gas, so the nitrogen content is less than 5 times and the activation of Mg is hindered. The growth atmosphere and the growth atmosphere in which the amount of nitrogen is more than 2000 times and which hinders the decomposition of the raw material gas of Mg can be excluded, so that the above-described operational effects can be easily and reliably achieved, and the stability of the manufacturing process can be improved. Can be improved.

Further, according to this embodiment, p-type In _x A
_{l y Ga z B 1-xyz} N m P n As 1-mn (0 <x, 0
≦ y, 0 ≦ z, 0 <x + y + z ≦ 1, 0 <m, 0 ≦ n,
(Including 0 <m + n ≦ 1) The growth temperature of the layer is 500
C. to 1230.degree. C., the temperature range is lower than 500.degree. C. and p-type conduction is not obtained during growth, and the temperature range is higher than 1230.degree. C. and good crystal is not obtained. Since it is possible to exclude and, it is possible to easily and surely obtain the above-described operational effects, and it is possible to improve the stability of the manufacturing process.

The stability of the manufacturing process of this embodiment is as shown in FIGS. 11 to 14.

That is, according to this embodiment, the in-plane distribution of the film thickness is significantly improved, so that the yield and reliability can be improved. In addition, this embodiment is
Since the growth temperature has little dependency on the growth temperature, each growth (run to r
Un), the variation in film thickness can be greatly reduced, and the reproducibility can be improved in addition to the above-mentioned yield and reliability.

Further, according to the present embodiment, the dependence of the acceptor concentration in the p-type conductive layer on the growth temperature can be greatly improved as compared with the prior art, so that variations in the acceptor concentration within the wafer surface or between the growth (run to run) can be suppressed. It can be reduced and reproducibility, yield and reliability can be improved.

Further, according to the present embodiment, the Al composition distribution of the GaAlN layer used for the current injection layer can be greatly improved as compared with the prior art, so that the reproducibility, the yield and the reliability can be improved.

Furthermore, the present embodiment is different from the conventional one in that
The growth temperature can be lowered by about 40 to 60 ° C. That is, conventionally, a low-temperature-grown InGaN-based active layer has a particularly high In composition, and when a high-temperature-grown p-type current injection (clad) layer and a p-type contact layer are formed on the upper portion of the InGaN-based active layer, it is altered by the high temperature. Therefore, there is a problem that the crystal quality is deteriorated. On the other hand, in the present embodiment, since the growth temperature can be lowered, such a problem can be solved and the quality of the active layer can be maintained.

(Second Embodiment) Next, a semiconductor laser according to the second embodiment of the present invention will be described.

FIG. 15 is a sectional view showing the structure of this semiconductor laser. This semiconductor laser has a sapphire substrate 31.
On top, a buffer layer 32, an n-type GaN layer 33, and an n-type AlG
aN current injection layer 34, GaN layer 35, active layer region 36 of multiple quantum well structure (MQW), GaN layer 37, p-type Al
The GaN current injection layer 38 is formed.

Here, the n-type AlGaN current injection layer 34 to the p-type AlGaN current injection layer 38 form a double hetero structure having a buried mesa structure using a high-resistance GaN layer 39.

Further, a p-type GaN layer 40 and a p-type GaN contact layer 41 are formed on the p-type AlGaN current injection layer 38 and the high resistance GaN layer 39.

A p-side electrode 43 is formed on the p-type GaN contact layer 41. An n-side electrode 42 is formed on the n-type GaN layer 33 which is partially exposed by etching or the like.

Next, the manufacturing method and operation of the above semiconductor laser will be described.

First, the sapphire substrate 31 is washed with an organic solvent and an acid, and then placed on the heatable susceptor of the MOCVD apparatus. Next, while flowing hydrogen at a flow rate of 20 L / min, the surface of the sapphire substrate is vapor-phase etched at a temperature of 1200 ° C. for about 10 minutes. Next, the temperature is lowered to 550 ° C., and the buffer layer 32 is formed on the sapphire substrate 31. Next, the temperature is raised to 1100 ° C., hydrogen is 15 L / min, nitrogen is 5 L / min, TMG is 100 cc / min, ammonia is 10 L / min, and silane is 5 L / min.
The n-type Ga is supplied at a flow rate of cc / min for about 1 hour each.
The N layer 33 is formed to a thickness of about 2 μm.

While maintaining the temperature at 1100 ° C., a TMA flow rate of 50 cc / min for about 15 minutes was applied to the n-type AlGaN current injection layer 34 to a thickness of about 500 nm.
, The TMA supply is stopped again,
The GaN layer 35 is formed to a thickness of about 200 nm by supplying for about 10 minutes.

Next, the supply of TMG is stopped and the substrate temperature is lowered to 780 ° C. TMG is 10 at this temperature
cc / min, ammonia 10 L / min, hydrogen 30 cc / min
Minute, nitrogen is flowed at about 19.7 L / minute, and the TMI is about 1.1 at a combination of a flow rate of 140 cc / minute and 15 cc / minute.
The active layer region 36 of the multi-quantum well structure (MQW) is formed by repeatedly switching and supplying each 5 minutes for 20 times and finally supplying 15 cc / min for 3 minutes.

Next, hydrogen was 40 cc / min and nitrogen was 19.
The temperature is raised to 1100 ° C. over 4 minutes while flowing ammonia at a flow rate of 96 L / min and 10 L / min. Since the active layer region is etched when the atmosphere at the time of temperature rise is hydrogen, the atmosphere in this process is preferably nitrogen.

Next, the temperature is maintained at 1100 ° C., hydrogen is 500 cc / min, nitrogen is 14.5 L / min, and TMG is 1
00 cc / min, 10 L / min of ammonia and 50 cc / min of Cp ₂ Mg are supplied for about 10 minutes to form the GaN layer 37 with a thickness of about 200 nm.

TMA is added to this at a flow rate of about 50 cc / min.
The p-type AlGaN current injection layer 38 is formed to a thickness of about 500 nm by being applied for 5 minutes. However, hydrogen was used as the carrier gas of the organometallic raw material when forming the p-type layer. In this state, the temperature is lowered to room temperature, taken out from the MOCVD apparatus, and the width of the surface is reduced by 20 in a well-known thermal CVD apparatus.
A μm SiO ₂ film is formed. Next, the wafer is RI
Placed in the E apparatus, the opening is etched away by BCl ₃ gas to the mesa structure. The wafer thus manufactured is again placed on the susceptor in the MOCVD apparatus and heated to 1100 ° C. in 30 L / min of nitrogen.

Next, at a temperature of 1100.degree.
c / min, nitrogen 14.5 L / min, TMG 100 cc /
Min, ammonia 10 L / min, DMZ (dimethyl zinc) at a flow rate of 50 cc / min for about 1 hour, i-type G
The aN layer 39 allows the n-type AlGaN current injection layer 34 to p
The embedded structure extends up to the AlGaN current injection layer 38.
Although such an i-type GaN layer is formed by growth after mesa etching in the present embodiment, it can be formed by ion implantation of hydrogen, oxygen or the like without etching removal. For example, 200 keV for hydrogen,
It can be realized by implanting 1 × 10 ¹⁴ cm ^-2 .

Next, while maintaining the temperature at 1100 ° C., hydrogen was flowed at 30 L / min for about 1 minute to produce p-type AlGa.
The SiO ₂ remaining on the N current injection layer 38 is removed by etching.

Next, while maintaining the temperature at 1100 ° C., the main carrier gas was switched from hydrogen to nitrogen, and hydrogen was 500 cc / min, nitrogen was 14.5 L / min, TMG was 100 cc / min, and ammonia was 10 L. / Min, Cp ₂ Mg
Is supplied at a flow rate of 50 cc / min for about 27 minutes, and p-type G
The aN layer 40 is formed to a thickness of about 900 nm. Furthermore, the flow rate was increased to 150 cc / min for Cp ₂ Mg, and 3
By being supplied for a minute, the p-type GaN layer 41 is formed with a thickness of 100 nm. This layer could realize a p-type crystal without requiring a post-process such as heat treatment. Furthermore, when growing these layers 40 and 41, 3 × 10 ¹⁶ cm ⁻³
By adding a certain amount of Zn, the carrier inactivation mechanism was reduced, and the carrier concentration was increased about twice.

Next, the supply of TMG and Cp ₂ Mg is stopped, and the substrate temperature is lowered to room temperature. However, 110
From 0 ℃ to 350 ℃, hydrogen 500cc / min, nitrogen 1
4.5 L / min and 10 L / min of ammonia are continuously supplied, and the supply of ammonia is stopped at 350 ° C.

The laser structure thus formed is
The n-type GaN layer 33 is taken out from the MOCVD apparatus and then, by a well-known vacuum deposition method or sputtering method, P
t (thickness 50 nm), Ni (thickness 50 nm), and Au (thickness 2 μm) were formed in this order to form the n-side electrode 42 having good ohmic contact. On the other hand, Pd (thickness: 20 nm) and Ti (thickness: 30 n) are sequentially provided on the p-type GaN layer 41 side.
m), Pt (thickness: 20 nm), and Au (thickness: 2 μm) are formed and subjected to heat treatment in nitrogen at 500 ° C. for 1 minute to form an ohmic p-side electrode 4 of about 7 × 10 ⁻³ Ωcm ^2.
It was set to 3. Here, the electrodes described above were used,
Metals listed above and Al, Sc, Mg, Si, Cr
It is possible to use a laminated structure or an alloy layer.

Next, this laser structure was cleaved from the substrate side by a scriber or the like to form a resonator mirror. The semiconductor laser thus manufactured has a wavelength of 42
It oscillated continuously at 0 nm. The operating voltage of this device was 4.7 V and the threshold current density was 3 kA / cm ² .

As described above, according to the second embodiment,
In addition to the effects of the first embodiment, a blue semiconductor laser having an internal current constriction structure can be realized.

As a modification of the second embodiment,
Some change the switching timing of the main carrier gas when forming the two p-type GaN layers 40 and 41. That is,
Under the growth conditions described above, when the lower p-type GaN layer 40 is formed, the main carrier gas remains hydrogen, and the main carrier gas is switched to nitrogen before the uppermost p-type GaN layer 41 is formed. Even if this p-type GaN layer 41 is formed, a high Mg activation rate can be obtained as in the present invention.

The reason is that even if Mg is not activated when the lower p-type GaN layer 40 is formed, the uppermost p-type GaN layer 4 is formed.
Since the growth temperature is as high as 1100 ° C. at the time of forming 1, the certain heat treatment effect is presumed to act on the lower p-type GaN layer 40. In addition, the upper p-type GaN layer 4
Since 1 is originally formed in a nitrogen atmosphere, it goes without saying that the activation rate of Mg is high.

(Third Embodiment) Next, a light emitting diode according to a third embodiment of the present invention will be described.

FIG. 16 is a sectional view showing the structure of this light emitting diode. This light emitting diode is an n-type 2H-type S
It has an iC substrate 51, and GaN and Si are provided on the substrate 51.
A mixed layer 52 in which C and 1: 9 are mixed is formed, and the n-type GaN layer 53 and the n-type InGaN light emitting layer 5 are formed on the mixed layer 52.
4, the p-type GaN layer 55 is laminated in this order. The dopants used are Si for the n-type GaN layer 53 and p-type G.
The aN layer 55 is Mg. Nitrogen is used as a main carrier gas only during the growth of the n-type InGaN layer 54 and the p-type GaN layer 55, ammonia and an organic Ga raw material are used as raw material gases, and an organic Mg raw material is used as a p-type dopant. Further, hydrogen is used as a carrier gas for the organic Mg raw material.

On the other hand, the n-type InGaN layer 54 and the p-type GaN
Hydrogen is used as a main carrier gas when growing layers other than the layer 55. The carrier concentration of each of the p-type and n-type GaN layers 55 and 53 is 2 × 10 ¹⁸ cm ⁻³ .

An n-side electrode 56 is formed on the SiC substrate 51, and a p-side electrode 57 is formed on the p-type GaN layer 55.

N and p were added to the multilayer film thus obtained.
When the light emitting diode was manufactured by forming the electrodes, the contact life of the p-side electrode was reduced, and the device life was improved to about 5 times that of the conventional one, and the reliability was greatly improved, as described above. .

(Fourth Embodiment) Next, a semiconductor laser according to a fourth embodiment of the present invention will be described with reference to FIG.

That is, the present embodiment is based on a specific example (first
In addition to the above embodiment), nitrogen in a plasma state is supplied by using any one of a low pressure growth method, a photoexcitation method, and a cracking method to form the p-type AlGaN current injection layer 18 and the p-type GaN contact layer 19. Is.

Specifically, for example, as described above, after the GaN optical guide layer 17 is formed, the main carrier gas is switched from hydrogen to nitrogen, and TMG, TMA, and hydrogen gas as a carrier gas for these source gases are used. Supply is stopped.

Then, by any of the above-mentioned methods, the substrate temperature is lowered until the state where the supply of active nitrogen atoms is achieved, NH ₃ is continuously supplied, and the like, and the growth already formed on the substrate is performed. Dissociation of Ga, In, N, etc. from the layer is suppressed.

Next, a fixed amount of nitrogen gas and the above-mentioned raw material gas are introduced, and the reaction chamber is adjusted to a predetermined pressure by adjusting the exhaust speed and the like.

Here, the p-type AlGaN current injection layer 18 and the p-type GaN contact layer 19 are sequentially formed by the plasma generated in the reaction chamber.

After that, the supply of the source gas is stopped and the substrate temperature is naturally lowered.

The following electrode forming steps are the same as those described above, and a blue semiconductor laser is formed.

This blue semiconductor laser was capable of continuous oscillation at room temperature with a low threshold current of about 30 mA.

As described above, according to the fourth embodiment,
Using active nitrogen atoms such as nitrogen plasma, p-type AlGa
By forming the N current injection layer 18 and the p-type GaN contact layer 19, the nitrogen vacancy density can be reduced, and the Mg content of G
By easily entering the site a, it was possible to obtain the same or higher effects as those of the first embodiment.

Further, by supplying nitrogen atoms in the active layer, the amount of ammonia used can be reduced, whereby the activation rate of Mg in the film can be further improved and the production cost can be greatly reduced.

It should be noted that, by setting the atmosphere to about several Torr or less, many voids were generated at N sites in Ga (Al) N, and Mg was easily introduced into the N sites to be inactivated. Can also be considered. However, according to this embodiment, since the nitrogen plasma is used, Ga (A
l) The number of N-site vacancies in N is reduced and Mg becomes Ga.
Since it entered the site and was activated, the room temperature continuous oscillation of the blue semiconductor laser could be realized.

The present embodiment is also applicable to the p-type GaN layers 40 and 41 according to the second embodiment and the p-type GaN layer 55 according to the third embodiment. That is, even if these p-type GaN layers 40, 41, 55 are formed by using plasma, the activation rate of Mg can be improved similarly to the present embodiment. Moreover, as plasma,
Any of DC plasma, high frequency plasma, and microwave plasma may be used.

(Fifth Embodiment) The above is each of the embodiments in which the p-type GaN-based semiconductor layer containing no In is used as the contact layer with the electrode. Next, as the fifth to ninth embodiments, a GaN-based semiconductor containing In (In _x Al _y
Ga _z B _1-xyz N _m P _n As _1-mn (0 <x, 0 ≦
y, 0 ≦ z, 0 <x + y + z ≦ 1, 0 <m, 0 ≦ n, 0
Each embodiment will be described in the case of using a layer <m + n ≦ 1)) as a contact layer with an electrode. Note that the principle embodiment will be described first, and then the specific embodiment will be described. Further, since the substrate temperature, the flow rate of the carrier gas, and the like are the same as those in the above-described first and second embodiments, detailed description thereof will be omitted in each of the following embodiments.

FIG. 17 is a sectional view showing the principle of the layer structure of a nitride semiconductor device according to the fifth embodiment of the present invention. The nitride-based semiconductor element, on the sapphire substrate 61, n-type GaN (In _x Al _y Ga at _1-xy N x = y
= 0) layer 62, p-type GaN layer 63, p-type InGaN (I
at _{n x Al y Ga 1-xy} N, 0 <x <1,0 = y) layer 64 are sequentially formed. According to this structure,
A pn junction is formed by the p-type GaN layer 63 and the n-type GaN layer 62.

(Impurity Concentration Distribution in the Depth Direction) For the structure of the present invention shown in FIG. 17, as shown in FIG.
By the IMS analysis, each concentration distribution of Mg and hydrogen (H) was investigated along the depth direction of the growth layer. For comparison, the impurity concentration distribution was examined along the depth direction of the conventional structure in which the p-type InGaN layer 64 was omitted from the structure of the present invention, as shown in FIG. 18 (b).

As a result, as can be seen from both figures, p-type G
When the Mg concentration of both the aN layer 63 and the p-type InGaN layer 64 is 5 × 10 ¹⁹ cm ⁻³ , the p concentration obtained by the conventional (manufacturing method) structure is increased.
The hydrogen concentration of the p-type GaN layer is 8 × 10 ¹⁹ cm ⁻³ , whereas the p-type InGaN layer 64 and the p-type Ga of the structure of the present invention are used.
The hydrogen concentration of both layers of the N layer 63 is 6 × 10 ¹⁹ cm ⁻³ .
This value is 75 in nitrogen after the growth of the conventional p-type GaN layer.
It is almost the same value as the hydrogen concentration after the heat treatment at 0 ° C. for 30 minutes.

Although not shown, the p-type InGaN layer 64 has an oxygen concentration near the surface of 5 × 10 ¹⁸ cm ⁻³ or less and a carbon concentration near the surface of 5 × 10 ¹⁹ cm ⁻³ or less. Then, they were substantially uniform within a range of ³ to 10 × 10 ¹⁷ cm ⁻³ from the position deeper than 100 nm from the outermost surface toward the substrate side. That is, the resistance was sufficiently low not only near the surface but also inside the element. On the other hand, in the conventional p-type GaN layer, both the oxygen concentration near the surface and the carbon concentration near the surface were higher by one digit or more.

(C-V measurement) FIG. 19 is a diagram showing the results of measuring the substantial acceptor concentration by C-V measurement for the above SIMS analysis samples. P-type I of the structure of the present invention
Since the nGaN layer 64 grows in a nitrogen-rich atmosphere,
Even as grown, the p-type layer has a low resistance. At this time, the p-type GaN layer 63 is, as shown,
It becomes a low resistance p-type layer at wn, and its value (5.4 × 10 ¹⁸
cm ⁻³ ) is a p-type GaN layer (as grow) having a conventional structure.
n is high resistance), and is substantially equal to the value obtained after heat treatment in a nitrogen atmosphere after growth. That is, since the p-type InGaN layer 64, which is a semiconductor layer containing In, is provided in the upper layer, the p-type InGaN layer 64 in the lower layer is formed.
Uptake of hydrogen into the n-type GaN layer 63 is suppressed, and M
It is thought that the activation of g is promoted.

(Modified Structure) In the structure of the present invention shown in FIG. 17, as shown in FIG. 20, n-type InGaN (In _x Al _y Ga _1-xy N) is used instead of the p-type InGaN layer 64. <X <1, 0 = y) The layer 65 may be provided as the uppermost layer.

Further, in the structure of the present invention, a p-type InGaN layer having a lower In component ratio than the p-type InGaN layer 64 is provided between the p-type GaN layer 63 and the p-type InGaN layer 64, so that the structure can be easily formed. Lattice matching may be performed.

As shown in FIG. 21, the undoped i
P-type GaN layer 63 and n-type G sandwiching the n-type InGaN layer 66
You may form a pin junction with the aN layer 62. The present invention may apply either a pn junction or a pin junction.

Further, as shown in FIG. 22, in order to improve the surface morphology, the n-type GaN layer 62 and the sapphire substrate 6 are formed.
1 and the GaN buffer layer 71, undoped or n
The --type GaN layer 72 may be formed. Further, an n-type AlGaN layer 73 is formed below the undoped i-type InGaN layer 66.
To form a p-layer on the undoped i-type InGaN layer 66.
The type AlGaN layer 74 may be formed, and a pin junction may be formed between the AlGaN cladding layers 73 and 74 and the undoped i-type InGaN layer 66.

(Sixth Embodiment) FIG. 23 shows a sixth embodiment of the present invention.
FIG. 3 is a cross-sectional view showing the theoretical configuration of the nitride-based semiconductor element according to the embodiment of FIG. This nitride-based semiconductor device has a current constriction structure, and is formed on a sapphire substrate 81 with an undoped GaN base layer 82, an n-type GaN contact layer 83, an undoped InGaN active layer 84, and a p-type G.
The aN current injection layer 85 is sequentially formed.

Further, on the p-type GaN current injection layer 85,
A plurality of n-type GaN current confinement layers 86 are selectively formed. In addition, on the p-type GaN current injection layer 85 and the n-type Ga
A p-type InGaN contact layer 87 is formed on the N-current confinement layer 86.

Next, the manufacturing method and operation of the nitride semiconductor device having the above current constriction structure will be described.

This nitride semiconductor device is shown in FIG.
As shown in FIG. 2, the undoped GaN layer 82 and the n-type Ga are formed on the sapphire substrate 81 by the first MOCVD growth.
The N layer 83, the undoped GaN active layer 84, the p-type GaN current injection layer 85, and the n-type GaN current confinement layer 86 are continuously formed in the same chamber. After that, FIG.
As shown in (b), the n-type GaN current confinement layer 86 is partially removed by etching. Then, as shown in FIG. 24C, the p-type InGaN contact layer 87 is formed by the second MOCVD growth (regrowth).

The p-type dopant is Mg or Zn.
Is used.

According to the above manufacturing method, the p-type InGaN contact layer 87 formed by re-growth has a low oxygen concentration and a low carbon concentration as described above, and is a p-type layer having a low resistance without heat treatment. Become.

Of the p-type GaN current injection layer 85 grown for the first time, the upper n-type GaN current blocking layer 8 is formed.
The part where 6 was removed, that is, the part where the surface was exposed in the chamber at the time of regrowth was a p-type low resistance layer with an acceptor concentration of 3 × 10 ¹⁸ cm ⁻³ as a result of CV measurement ( S
As a result of IMS analysis, the Mg concentration was 2 × 10 ¹⁹ cm ⁻³ ).

On the other hand, of the p-type GaN current injection layer 85,
The portion covered with the n-type GaN current blocking layer 86 did not have the p-type low resistance during the regrowth.

As described above, according to the present embodiment, since the p-type InGaN contact layer 87 is formed by re-growth, a low-resistance p-type layer can be obtained without the need for heat treatment, and the current constriction is further promoted. Can be made.

(Modified Structure) The structure of this embodiment is as follows.
As shown in FIG. 25, the GaN buffer layer 82 a is provided between the sapphire substrate 81 and the undoped GaN base layer 82.
May be provided. In addition, as shown in FIG. 25, an undoped InGaN active layer 84 and an n-type GaN contact layer 83.
And an n-type AlGaN current injection layer 91 are provided between them and the p-type GaN current injection layer 85.
The N current injection layer 95 may be provided. Further, in either the p-type GaN current injection layer 85 or the p-type AlGaN current injection layer 95, the n-type GaN current confinement layer 86 or the n-type InGaN is formed.
Any of the current confinement layers can be used.

(Seventh Embodiment) FIG. 26 shows a seventh embodiment of the present invention.
FIG. 26 is a cross-sectional view showing the configuration of the semiconductor laser according to the embodiment of the present invention, in which the same parts as those in FIGS. 24A to 24C and FIG. This semiconductor laser includes a GaN buffer layer 82a, an undoped GaN base layer 82, an n-type GaN contact layer 83, and a GaN buffer layer 82a on a sapphire substrate 81.
n-type AlGaN current injection layer 91, undoped GaN guide layer 92, MQW-structured undoped AlGaN active layer 9
3, a p-type GaN guide layer 94, a p-type AlGaN current injection layer 95, and a p-type GaN current injection layer 85 are sequentially formed.

On the p-type GaN current injection layer 85, n-type G
The aN current confinement layer 86 is selectively formed. Also,
A p-type InGaN contact layer 87 is formed on the p-type GaN current injection layer 85 and the n-type GaN current confinement layer 86.

P is formed on the p-type InGaN contact layer 87.
The side electrode 97 is formed. An n-side electrode 96 is formed on the n-type GaN contact layer 83 which is partially exposed by etching or the like.

Next, the manufacturing method and operation of the above semiconductor laser will be described.

As shown in FIG. 27 (a), undoped GaN (In _x Al _y Ga _1-xy N) with a thickness of 50 nm is formed on the sapphire substrate 81 by MOCVD, and x = y =
0) buffer layer 82a, 2 μm thick undoped GaN base layer 82, 4 μm thick n-type GaN contact layer 83,
0.3 μm thick n-type Al _q Ga _1-q N (0 ≦ q ≦ 1) current injection layer 91, 0.1 μm thick undoped GaN guide layer 92, In _x Ga _y Al _1-xy N Undoped In consisting of multiple quantum well structure with thickness of 0.1 μm
GaN active layer 93, 0.1 μm thick p-type GaN guide layer 94, 0.3 μm thick p-type Al _q Ga _1-q N (0 ≦ q ≦
1) Current injection layer 95, 0.5 μm-thick p-type GaN current injection layer 85, 1 μm-thick n-type GaN (Al _q Ga _1-q N q = 0) current confinement layer 86 is formed by continuous growth. .

The n-type impurity density is monosilane (S
It is appropriately controlled by the introduction of iH ₄ ). Similarly, the p-type impurity density is appropriately controlled by introducing biscyclopentadienyl magnesium (Cp ₂ Mg).

Next, as shown in FIG. 27B, n-type G
The aN current constriction layer 86 is partially patterned, and the n-type GaN current confinement layer 86 is partially removed by etching or the like so that the p-type GaN current injection layer 85 is exposed at the outermost surface.

On the p-type GaN current injection layer 85 and the n-type GaN current confinement layer 86, as shown in FIG. 27C, a p-type In layer having a thickness of 1.5 μm was formed by MOCVD.
GaN (In _x Al _y Ga _1-xy N, 0 <x ≦ 0.
3, y = 0) The contact layer 87 is formed. At this time, the growth temperature is 750 ° C. to 1100 ° C., hydrogen is used as the carrier gas of the source gas, and nitrogen gas is used as the main carrier gas.

Here, the obtained wafer was taken out of the MOCVD furnace, partially masked with SiO ₂ or the like, and etched to a depth reaching the n-type GaN contact layer 83 as shown in FIG. 28 (a). It

Next, the sapphire substrate 81 is formed to a thickness of about 100 μm by polishing the surface opposite to the side on which the GaN-based semiconductor layers 82a to 95 are deposited.

As shown in FIG. 28B, an n-type GaN contact layer 83 made of a metal such as Ti-Au is formed on the n-type GaN contact layer 83.
The side electrode 96 is formed. After that, mask SiO ₂
Etc. are removed, and as shown in FIG. 28C, p-type InG
On the aN contact layer 87, for example, Pt, Ti / Au, N
A p-side electrode 97 made of i or the like is formed.

Here, the p-type InGaN contact layer 87 has a surface oxygen concentration of 5 × 10 ¹⁸ cm ⁻³ or less and a surface carbon concentration of 5 × 10 ¹⁹ cm ⁻³ or less, which is low resistance and good. Had a good ohmic contact.

The wafer thus obtained is cut into a suitable size by scribing, cleaving, or dry etching to obtain a large number of chips. Then, these chips are mounted on a predetermined stem (wire frame), and after wire bonding and molding, the GaN laser of the present invention is completed.

This semiconductor laser has an emission wavelength of 400 nm.
It was possible to obtain good characteristics that oscillate at a low threshold.

As described above, according to this embodiment, the process can be simplified as compared with the conventional case. That is, according to this embodiment, hydrogen is taken into the p-type cladding layer and the p-type contact layer only by adding a simple step of growing a p-type InGaN-based semiconductor layer to the conventional continuous epitaxial growth. Inactivation of the acceptor can be suppressed.

Therefore, since the heat treatment and the like are substantially eliminated, the number of manufacturing steps is reduced. Further, it is possible to eliminate the factors that cause deterioration of device characteristics due to surface contamination and diffusion of impurities in the crystal due to a heat treatment after growth.

Further, since the oxygen concentration and carbon concentration on the surface can be reduced, a good ohmic contact with low resistance can be formed, and the operating voltage can be lowered.
It was possible to obtain a semiconductor laser with good characteristics that oscillates at a low threshold value (low operating voltage) at m.

Furthermore, the type of p-type dopant (Mg
Etc.), the film thickness of the p-type InGaN contact layer 87 (50 n
m-1500 nm) and the component ratio x of In (0 <x ≦ 0.
3), the type of carrier gas (raw material gas containing hydrogen gas and ammonia, carrier gas consisting of nitrogen gas), flow rate (nitrogen gas: hydrogen gas = 5 to 2000: 1), etc. are within appropriate ranges. The effect of can be easily and surely realized, and the element characteristics and the stability of the manufacturing process can be improved.

(Modified Structure) The seventh embodiment of the present invention may have a structure in which the p-type GaN current injection layer 85 in the first growth is omitted as shown in FIG. In this case, the layer formed by the second growth may have a two-layer structure of a p-type GaN layer 85a and a p-type InGaN contact layer 87, as shown in FIG.

(Eighth Embodiment) Next, a semiconductor laser according to an eighth embodiment of the present invention will be described.

FIG. 31 is a sectional view showing the principle structure of this semiconductor laser, and the same parts as in FIG. This semiconductor laser has a refractive index guided structure, and includes an undoped GaN base layer 82 and an n-type GaN contact layer 8 on a sapphire substrate 81.
3, an undoped InGaN active layer 84 and a p-type GaN current injection layer 85 are sequentially formed.

The p-type GaN current injection layer 85 has a ridge formed by selective etching. In addition, p-type GaN
The current injection layer 85 has a plurality of n-type I on a portion other than the ridge.
An nGaN current / light confinement layer 98 is selectively formed. In addition, on the ridge of the p-type GaN current injection layer 85 and n
A p-type InGaN contact layer 87 is formed on the type InGaN light confinement layer 98.

Next, the manufacturing method and operation of the semiconductor laser having the above-described refractive index guided structure will be described.

In this semiconductor laser, as shown in FIG. 32A, the undoped GaN layer 82, the n-type GaN layer 83, the undoped GaN active layer 84, and the p-type GaN are formed on the sapphire substrate 81 by the first growth. Layers 85 are successively formed in the same chamber. Then, FIG. 32 (b)
The p-type GaN layer 85 is partially etched away to form a ridge, as shown in FIG. Further, as shown in FIG. 32C, a mask 99 of SiO ₂ or the like is formed on this ridge.
Is formed. Next, the n-type InGaN layer 98 is selectively grown on the p-type GaN layer 85 other than the mask 99 such as SiO ₂ by re-growth (second growth). After that, the mask 99 is removed, and the third growth is performed, so that FIG.
, The p-type InGaN layer 87 is replaced by the p-type GaN layer 8
5 and the n-type InGaN layer 98.

Even with the refractive index guided structure as described above,
Similar to the current confinement structure, p-type InGaN contact layer 87
Has a low oxygen concentration and a low carbon concentration to obtain a good ohmic contact with a low resistance.
It is possible to obtain good characteristics of oscillating at a low threshold value at m.

(Modified Structure) The structure of this embodiment is as follows.
As shown in FIG. 33, the GaN buffer layer 82 a is provided between the sapphire substrate 81 and the undoped GaN base layer 82.
May be provided. In addition, as shown in FIG. 33, an undoped InGaN active layer 84 and an n-type GaN contact layer 83.
And an n-type AlGaN current injection layer 91 are provided between them and the p-type GaN current injection layer 85.
The N current injection layer 95 may be provided.

When the p-type AlGaN current injection layer 95 is provided, the n-type InGaN light confining layer 98 is replaced with n.
-Type GaN may be used as the optical confinement layer. That is, n
In the In _x Ga _1-x N (0 ≦ x ≦ 1) type light confining layer 98, the In component ratio x may be zero. In addition, n-type G
Needless to say, the n-type InGaN optical confinement layer 98 may be used for the p-type AlGaN current injection layer 95 without using aN.

(Ninth Embodiment) FIG. 34 shows a ninth embodiment of the present invention.
FIG. 34 is a cross-sectional view showing the structure of the semiconductor laser according to the embodiment of the present invention, in which the same parts as those in FIGS. 32 (a) to (d) and FIG. This semiconductor laser includes a GaN buffer layer 82a, an undoped GaN base layer 82, an n-type GaN contact layer 83, and a GaN buffer layer 82a on a sapphire substrate 81.
n-type AlGaN current injection layer 91, undoped GaN guide layer 92, MQW structure undoped InGaN active layer 9
3, a p-type GaN guide layer 94 and a p-type AlGaN current injection layer 95 are sequentially formed.

A ridge is formed on the p-type AlGaN current injection layer 95 by selective etching. p-type AlGa
In the N current injection layer 95, a plurality of n-type InGaN current light confinement layers 98 are selectively formed on a portion other than the ridge. Further, on the ridge of the p-type AlGaN current injection layer 95 and on the n-type InGaN optical confinement layer 98, p-type InGa is formed.
The N contact layer 87 is formed.

On the p-type InGaN contact layer 87, p
The side electrode 97 is formed. An n-side electrode 96 is formed on the n-type GaN contact layer 83 which is partially exposed by etching or the like.

Next, the manufacturing method and operation of the above semiconductor laser will be described.

Similarly to the above, as shown in FIG. 35 (a), 50 n is formed on the sapphire substrate 81 by MOCVD.
m-thick undoped GaN (In _x Al _y Ga _1-xy N with x = y = 0) buffer layer 82a, 2 μm thick undoped GaN underlayer 82, 4 μm thick n-type GaN contact layer 83, 0.3 μm thick n-type Al _q Ga _1-q N (0 ≦ q ≦
1) Current injection layer 91, 0.1 μm thick undoped GaN
Guide layer _{92, In x Ga y Al 1} -xy of N a multiple quantum well structure of total thickness 0.1μm undoped InGaN active layer 93,0.1Myuemu p-type GaN guide layer 94,0.3μm thick thickness P-type Al _q Ga _1-q N (0 ≦
q ≦ 1) The current injection layer 95 is formed by continuous growth.

Next, as shown in FIG. 35B, p-type A
l _q Ga _1-q N (0 ≦ q ≦ 1) Si on the current injection layer 95
Patterning and masking of the O ₂ layer 99 etc. are performed,
P-type Al _q Ga _1-q N (0 ≦ q ≦
1) The current injection layer 95 is selectively removed halfway to form a ridge.

Subsequently, as shown in FIG. 35C, n-type In _x is formed on the p-type Al _q Ga _{1 -q} N (0 ≦ q ≦ 1) current injection layer 95 except the ridge by selective growth. Ga _1-x N
The (0 ≦ x ≦ 1) light confinement layer 98 is formed by the second growth.

Further, the mask such as the SiO ₂ layer 99 on the ridge of the p-type AlGaN current injection layer 95 is removed. Further, by MOCVD, as shown in FIG. 36A, 1 μm is formed on the ridge of the p-type AlGaN current injection layer 95 and on the n-type InGaN light confinement layer 98 on both sides thereof.
The thickness of p-type InGaN of _{(In x Al y Ga 1-} xy N, 0
<X ≦ 0.3, y = 0) Layer 87 is formed. Note that, similarly to the above, the growth temperature at this time is 750 ° C. to 1000 ° C., hydrogen is used as the carrier gas of the source gas, and nitrogen gas is used as the main carrier gas.

Thereafter, in the same manner as described above, this wafer is shown in FIG.
As shown in (b), after selectively etching to a depth reaching the n-type GaN contact layer 83, a sapphire substrate 81 is formed by polishing or the like to have a thickness of about 100 μm.

Similarly, as shown in FIG. 36 (c),
An n-side electrode 96 is formed on the n-type GaN contact layer 83, and a p-side electrode 97 is formed on the p-type InGaN contact layer 87.
Is formed. The electrodes 96 and 97 can be formed of the same material as described above.

The wafer after completion of electrode attachment is formed into a large number of chips by cleavage, etc., as described above. Each chip is mounted on a predetermined stem (wire frame),
After wire bonding, it is molded and processed into a finished GaN-based laser.

This semiconductor laser is a p-type In similar to the above.
The GaN contact layer 87 had a low oxygen concentration and a low carbon concentration, had a low resistance and good ohmic contact, and could obtain good characteristics of oscillating at a low threshold at an emission wavelength of 400 nm.

As described above, according to this embodiment, the seventh
In addition to the effect of the embodiment described above, p-type Al _q Ga _1-q N (0 ≦
The ridge portion of the q ≦ 1) layer 95 and the film other than the ridge portion are appropriately determined, and the bandgap energy of the n-type In _x Ga _1-x N (0 ≦ x ≦ 1) layer 98 is set to the undoped InGaN active layer 93. By appropriately determining the composition x so as to be smaller than the band gap energy, it is possible to form not only a current confinement type structure but also a semiconductor laser having a refractive index guided structure.

(Tenth Embodiment) FIGS. 1, 15, and 1
6, a semiconductor laser having the structure shown in FIG. 28 is formed by ammonia gas (NH ₃ ) by metal organic chemical vapor deposition (MOCVD) method,
It is formed by using an organic metal raw material (TMG, TMA, TMI) and a dopant raw material (Cp ₂ Mg, SiH ₄ ).
However, the carrier gas used when forming only the layer having p-type conductivity or all the layers for the device including the layer having n-type conductivity is CO, CO _{2 at} a concentration of 0.1 to 10 vol p.
The carrier gas is an inert gas of pb. CO, C
When the concentration of O ₂ is higher than this range, these impurities tend to be unevenly distributed on the outermost surface of the growth layer, and the contact resistance with the p-side electrode tends to increase. Also, CO, CO
_When the concentration of ₂ is lower than this concentration range, the effect of filling the nitrogen vacancy points (nitrogen vacancies) by oxygen or carbon is reduced, so that the nitrogen vacancies compensate the acceptor and the device has a high resistance.

Further, the group V raw material and the I
The supply amount (mol) ratio (V / III ratio) of the group II raw material is set to GaN.
3,000 or less for layer growth and 36 for GaAlN growth
00 or less, but 300 for growth of the InGaN-based semiconductor layer
00 or less. When the V / III ratio is equal to or more than the above value, the activation rate of Mg to acceptors or carriers decreases.

The acceptor concentration and carrier concentration of the p-type conductive layer in the nitride semiconductor device manufactured according to this embodiment are the same as those in the conventional example (Japanese Patent Application Laid-Open No. 8-325094, Japanese Patent Application No. 8-3295094).
No. 236744), and more than double that in the case of the above-described first to ninth embodiments, and as a result, the contact resistance between the p-type conductive layer and the p-side electrode can be reduced, and the operating voltage of the device can be greatly increased. In addition, the yield and reliability of the nitride-based semiconductor device can be significantly improved, because the amount can be stably reduced. Further, after the film formation, a post-treatment such as heat treatment is not required, and an element having better characteristics than the conventional one can be obtained, so that a great merit in terms of productivity and cost can be obtained as compared with the conventional manufacturing.

(Eleventh Embodiment) FIGS. 1, 15, and 1
6, a semiconductor laser having the structure shown in FIG. 28 is formed by ammonia gas (NH ₃ ) by metal organic chemical vapor deposition (MOCVD) method,
It is formed by using organic metal raw materials (TMG, TMA, TMI) and dopant raw materials (Cp ₂ Mg, SiH ₄ ).
However, the carrier gas used when forming only the layer having p-type conduction or all layers of the device multilayer film including the layer having n-type conduction was purified to a hydrogen (H ₂ ) concentration of 1 vol ppb or less. The carrier gas is made of a high-purity inert gas.
If the H ₂ concentration is higher than this range, the impurities tend to be unevenly distributed on the outermost surface of the growth layer, and the contact resistance with the p-side electrode tends to increase. Further, when the concentration of H ₂ is lower than this concentration range, the effect of filling the nitrogen vacancy points (nitrogen vacancies) by hydrogen is reduced, so that the nitrogen vacancies compensate the acceptors and the resistance of the device increases. .

In addition, when the p-type conductive layer is manufactured, the group V raw material and I are used.
The supply amount (mol) ratio (V / III ratio) of the group II raw material is Ga
3,000 or less for growing N layer, 3 for growing GaAlN
600 or less, but 30 for growth of InGaN-based semiconductor layer
000 or less. When the V / III ratio is equal to or more than the above value, the activation rate of Mg to acceptors or carriers decreases.

The acceptor concentration and carrier concentration of the p-type conductive layer in the nitride-based semiconductor device manufactured according to this embodiment are the same as those of the conventional example (Japanese Patent Laid-Open No. 8-325094, Japanese Patent Application No. 8-3295094).
No. 236744), and more than three times that in the case of the above-described first to ninth embodiments, as a result, the contact resistance between the p-type conductive layer and the p-side electrode can be reduced, and the operating voltage of the device can be greatly increased. In addition, the yield and reliability of the nitride-based semiconductor device can be significantly improved, because the amount can be stably reduced. Further, after the film formation, a post-treatment such as a heat treatment is not required, and an element having better characteristics than the conventional one can be obtained, so that a great advantage can be obtained in terms of productivity, cost and efficiency in comparison with the conventional manufacturing.

(Twelfth Embodiment) The structure of the semiconductor laser according to the first embodiment (shown in FIG. 1) is shown by ammonia gas, organic metal raw materials (TMG, TMA, TMI), and dopant raw material (Cp ₂ Mg). , SiH ₄ ) is used. However, when forming only the layer having p-type conductivity or all the layers of the device multilayer film including the layer having n-type conductivity, the carrier gas is nitrogen gas alone or nitrogen containing 2.5 vol% or less of hydrogen. It is formed by using gas.

After forming the p-GaN contact layer 19 on the outermost surface, only the supply of TMG is stopped, the substrate temperature is maintained as it is, and ammonia gas, Cp ₂ Mg and nitrogen carrier gas are supplied for 10 minutes. After that, the supply of CP ₂ Mg is stopped, the substrate temperature is lowered to 350 ° C., the supply of ammonia is also stopped at 350 ° C., and the nitrogen carrier gas alone is naturally cooled.

The acceptor concentration of the p-GaN contact layer 19 on the outermost surface of the obtained device was evaluated by CV measurement. As a result, after the growth of the p-GaN contact layer 19, only ammonia was continuously supplied up to 350 ° C. It was found that all of the raw materials of (1) were lower by one digit or more (up to 1 × 10 ¹⁷ cm ⁻³ ) as compared with the sample A obtained by the conventional method in which the supply was stopped and natural cooling was performed. However, when the IV characteristics of this sample were evaluated, the contact resistance was significantly improved compared to sample A, and the operating voltage of the device was about 112. According to the SIMS analysis, about 10 times as much Mg was present in the outermost surface of the p-GaN contact layer 19 as in the inside of the layer.

When the device characteristics of the obtained semiconductor laser were evaluated, room temperature continuous oscillation was performed at a wavelength of 405 nm, an operating voltage of 4.5 V and a threshold current of 37 mA.

(Thirteenth Embodiment) In the same structure and film forming method as in the twelfth embodiment, p-GaN on the outermost surface is used.
After forming the contact layer 19, only the supply of TMG is stopped, the substrate is naturally cooled under the supply of ammonia until the substrate temperature reaches 800 ° C., and when the substrate temperature reaches 800 ° C., the ammonia supply is stopped, and CP ₂ Mg is added. And nitrogen carrier gas only for 15 minutes. After that, the supply of CP ₂ Mg is stopped, and natural cooling is performed with only the nitrogen carrier gas being supplied.

When the acceptor concentration of the p-GaN contact layer 19 on the outermost surface of the obtained device was evaluated by CV measurement, only ammonia was continuously supplied to 350 ° C. after the growth of the p-GaN contact layer 19, and other All of the raw materials of No. 1 were the same as those of Sample A obtained by the conventional method of stopping the supply and naturally cooling. When the IV characteristics of this sample were evaluated, the contact resistance was improved as compared with sample A, and the operating voltage of the device was about 3/5. By SIMS analysis, p
On the outermost surface of the -GaN contact layer 19, about 5 times as much Mg as inside the layer existed.

When the device characteristics of the obtained semiconductor laser were evaluated, room temperature continuous oscillation was performed at a wavelength of 410 nm, an operating voltage of 5.5 V and a threshold current of 45 mA.

(Fourteenth Embodiment) In the same structure and film forming method as in the twelfth embodiment, p-GaN on the outermost surface is used.
After forming the contact layer 19, only the supply of TMG is stopped, the substrate is naturally cooled under the supply of ammonia until the substrate temperature reaches 900 ° C., and when the substrate temperature reaches 950 ° C., the ammonia supply is stopped and CP ₂ Mg is added. Then, the temperature of the slope is lowered while supplying nitrogen carrier gas to 750 ° C. for 10 minutes. CP ₂ when substrate temperature reaches 700 ℃
The supply of Mg is stopped, and natural cooling is performed in the state where only the nitrogen carrier gas is supplied.

The acceptor concentration of the p-GaN contact layer 19 on the outermost surface of the obtained device was evaluated by CV measurement. As a result, after the growth of the p-GaN contact layer 19, only ammonia was continuously supplied up to 350 ° C. As for the raw material, the acceptor concentration equivalent to that of the sample A obtained by the conventional method of stopping the supply and naturally cooling was obtained. Further, when the IV characteristics of this sample were evaluated, the contact resistance was significantly improved compared to sample A, and the operating voltage of the device was reduced to about 1/4. As a result of SIMS analysis, about 20 times more Mg than the inside of the layer was present on the outermost surface of the p-GaN contact layer 19.

When the device characteristics of the obtained semiconductor laser were evaluated, continuous oscillation at room temperature with a wavelength of 407 nm, an operating voltage of 4.0 V and a threshold current of 32 mA was performed.

As shown in the above three embodiments (the twelfth to fourteenth embodiments), after the p-side contact layer on the outermost surface is formed, the supply of the film-forming raw material such as TMG is stopped and the Mg is emptied. It was shown that a low contact resistance can be realized by pouring.

(Fifteenth Embodiment) Even in the conventional method for manufacturing a semiconductor light emitting device in which the above three embodiments (twelfth to fourteenth embodiments) are formed by using a hydrogen carrier gas, Mg is grown for a predetermined time after growth. The effect of reducing the p-side contact resistance can be obtained by idling at a predetermined temperature or higher. However,
In the conventional method for manufacturing a semiconductor light emitting device using a hydrogen carrier gas, it is necessary to perform a heat treatment for activating Mg after manufacturing the device multilayer structure.

(Sixteenth Embodiment) The structure of the semiconductor laser according to the first embodiment (shown in FIG. 1) is a layered film for an element including only a layer having p-type conduction or a layer having n-type conduction. Ammonia gas and organometallic raw materials (T
MG, TMA, TMI), and dopant raw material (Cp ₂
It is formed by using Mg, SiH ₄ ). However, only a layer having p-type conductivity or a carrier gas for forming all layers of the device multilayer film is formed using only nitrogen gas or nitrogen gas containing 2.5% by volume or less of hydrogen.

On the uppermost p-GaN contact layer 19, a layer 23 having a superlattice structure in which p-GaN and p-In _0.2 Ga _0.8 N are alternately laminated with a film thickness of 2 nm or less is formed. Layer 2 having the p-type superlattice structure
After forming No. 3, only the supply of TMG is stopped, the substrate temperature is kept as it is, and ammonia gas, CP ₂ Mg and nitrogen carrier gas are supplied for 2 minutes. After that, the supply of CP ₂ Mg is stopped, the substrate temperature is lowered to 350 ° C.,
Then, the supply of ammonia is also stopped, and natural cooling is performed while supplying only the nitrogen carrier gas.

A part of the obtained multilayer structure for a semiconductor laser is a layer 23 having a superlattice structure in which p-GaN and p-In _0.2 Ga _0.8 N are alternately laminated from the outermost surface layer to the n-type Ga layer.
The n-type electrode 20 is formed on the GaN contact layer 13 exposed by the dry etching method to a depth reaching the N contact layer 13. Further, the SiO ₂ layer 2 for current confinement is formed on the layer 23 having the p-type superlattice structure in the part of the multi-layer structure which is not removed.
1 is selectively formed, and the p-type electrode 22 is formed on the SiO ₂ layer 21 and the layer 23 having the p-type superlattice structure.

When the device characteristics of the obtained semiconductor laser were evaluated, continuous oscillation at room temperature was performed at a wavelength of 405 nm, an operating voltage of 4.0 V and a threshold current of 30 mA. Due to the effect of the p-side contact layer 23 having a superlattice structure, low contact resistance can be realized.

(Other Embodiments) The present invention optimizes the combination of the carrier gas and the dopant in the manufacturing process to accelerate the activation of the dopant without heat treatment, and to improve the oxygen concentration on the outermost surface of the growth layer. Since the technique of optimizing the carbon concentration and reducing the contact resistance is used,
The present invention is not limited to the current confinement type structure or the refractive index guiding type structure of the double hetero (DH) structure illustrated, but also includes a homojunction structure and a single hetero (SH) structure other than the double hetero structure, and a double hetero structure. However, it goes without saying that other structures besides the current constriction type structure and the refractive index guiding type structure are included.

Further, the present invention uses L using a nitride semiconductor.
Not only light-emitting devices such as ED and LD, but also p-channel HE
Application to electronic devices such as MT or HBT is also possible.

Further, the same effect as the present invention can be obtained by using an inert gas such as argon (Ar) or helium (He) other than nitrogen as the main carrier gas.

In the above description, the carrier gas which substantially consists of an inert gas such as nitrogen is used during the growth of the p-type layer. However, when the nitride-based semiconductor element such as LED or LD is manufactured, It is possible to use a nitrogen carrier gas also during layer growth. That is, all layers during the growth of the device multilayer film can be formed by using an inert gas such as nitrogen as a main carrier gas.

The present invention can provide a nitride semiconductor device having sufficiently good characteristics without heat treatment after growth.
If desired, for example, to further improve the characteristics, a heat treatment may be applied after the growth. That is, the present invention does not prohibit heat treatment after growth. The present invention makes it possible to omit the heat treatment after growth.

Besides, the present invention can be variously modified and implemented without departing from the gist thereof.

[0241]

As described above, according to the present invention, I
_{n x Al y Ga z B 1} -xyz N m P n As 1-mn is the maximum value of the maximum value and the carbon concentration of the oxygen concentration near the surface of the p-type compound semiconductor layer, such as the average value of the oxygen concentration in a plane 5 times or less. Therefore, since there is no locally high oxygen concentration region in the wafer surface, non-uniform injection (current), generation of non-emission region, influence on waveguiding,
Besides, adverse effects on resistance, electromigration, distortion, thermal characteristics, etc. can be eliminated, and reliability can be further improved.

Further, the CO, CO ₂ and H ₂ concentrations in the carrier gas when the p-type compound semiconductor layer is grown, and the raw material supply ratio (V / III) are regulated. The p-type additive impurities are activated without a heat treatment step, and a p-type electrically conductive layer having a high acceptor concentration and carrier concentration is obtained, and the initial characteristics, reliability, productivity, and cost of the device are significantly improved. Furthermore, since the contact resistance with the p-side electrode is reduced, the operating voltage of the element can be reduced, and the initial characteristics, yield, and reliability of the element are significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a semiconductor laser according to a first embodiment.

FIG. 2 is a diagram showing the concentration distribution in the depth direction in the first embodiment in comparison with before and after heat treatment of a comparative example.

FIG. 3 is a photograph of a halftone image in which the in-plane distribution of carbon concentration in the same embodiment is displayed on a display.

FIG. 4 is a photograph of a halftone image in which an in-plane distribution of oxygen concentration in the same embodiment is displayed on a display.

FIG. 5 is a photograph of a halftone image in which the in-plane distribution of hydrogen concentration in the same embodiment is displayed on a display.

FIG. 6 is a photograph of a halftone image in which the in-plane distribution of silicon concentration is displayed on the display in the same embodiment.

FIG. 7 shows an in-plane distribution of carbon concentration in a comparative example (depth 10
(0 nm) is a photograph of a halftone image displayed on the display.

FIG. 8 is a photograph of a halftone image in which the in-plane distribution of oxygen concentration in Comparative Example is displayed on a display.

FIG. 9 is a photograph of a halftone image in which the in-plane distribution of hydrogen concentration in Comparative Example is displayed on a display.

FIG. 10 is a photograph of a halftone image in which the in-plane distribution of silicon concentration in Comparative Example is displayed on a display.

FIG. 11 is a view showing a wafer in-plane distribution of a growth rate in a GaN layer in comparison with a nitrogen carrier gas and a hydrogen carrier gas.

FIG. 12 is a diagram showing the growth temperature dependence of the growth rate in a GaN layer, comparing nitrogen carrier gas and hydrogen carrier gas.

FIG. 13 is a diagram showing the dependency of acceptor concentration on the growth temperature in a p-type conductive layer in comparison with a nitrogen carrier gas and a hydrogen carrier gas.

FIG. 14 is a diagram showing the in-wafer distribution of Al composition in a GaAlN layer used as a current injection layer in comparison between a nitrogen carrier gas and a hydrogen carrier gas.

FIG. 15 is a sectional view showing a structure of a semiconductor laser according to a second embodiment.

FIG. 16 is a sectional view showing a structure of a light emitting diode according to a third embodiment.

FIG. 17 is a sectional view showing the structure of a nitride-based semiconductor device according to a fifth embodiment.

FIG. 18 is a view showing an impurity concentration distribution in the depth direction in the same embodiment as compared with a conventional one.

FIG. 19 is a view showing a CV measurement result in the same embodiment in comparison with a conventional one.

FIG. 20 is a diagram showing a modified configuration of the same embodiment.

FIG. 21 is a view showing a modified configuration of the same embodiment.

FIG. 22 is a view showing a modified configuration of the same embodiment.

FIG. 23 is a cross-sectional view showing the theoretical structure of a nitride-based semiconductor device according to a sixth embodiment.

FIG. 24 is a manufacturing process diagram in the embodiment.

FIG. 25 is a view showing a modified configuration of the same embodiment.

FIG. 26 is a sectional view showing the structure of a semiconductor laser according to a seventh embodiment.

FIG. 27 is a manufacturing process diagram in the embodiment.

FIG. 28 is a manufacturing process diagram in the embodiment.

FIG. 29 is a view showing a modified configuration of the same embodiment.

FIG. 30 is a view showing a modified configuration of the same embodiment.

FIG. 31 is a sectional view showing the principle configuration of a semiconductor laser according to an eighth embodiment.

FIG. 32 is a manufacturing process diagram in the embodiment.

FIG. 33 is a view showing a modified configuration of the same embodiment.

FIG. 34 is a sectional view showing the structure of the semiconductor laser according to the ninth embodiment.

FIG. 35 is a manufacturing process drawing in the embodiment.

FIG. 36 is a manufacturing process diagram in the embodiment.

FIG. 37 is a schematic view showing the structure of a conventional blue semiconductor laser.

FIG. 38 is a diagram showing the concentration distribution in the depth direction before and after the conventional heat treatment.

[Explanation of symbols]

11, 31, 61, 81 ... Sapphire substrate 12, 82 ... Undoped GaN underlayer 13, 33, 62, 83 ... N-type GaN contact layer 14, 34, 91 ... N-type AlGaN current injection layer 15, 35 ... GaN optical guide Layers 16, 36, 66, 84, 93 ... InGaN active layer 17 ... GaN optical guide layer 18, 38 ... p-type AlGaN current injection layer 19, 41 ... p-type GaN contact layer 20, 42, 56, 96 ... n-side electrode 21 ... SiO ₂ layers 22, 43, 57, 97 ... P-side electrode 23 ... Superlattice layer 32 ... Buffer layer 37 ... GaN layer 38 ... P-type AlGaN current injection layer 39 ... High-resistance GaN layer 40 ... P-type GaN layer 51 ... n-type 2H-type SiC substrate 52 ... mixed layer 53 ... n-type GaN layer 54 ... n-type InGaN light-emitting layer 55 ... p-type GaN layers 63, 85 ... p-type GaN layers 64, 87 ... p-type In aN layer 65 ... n-type InGaN layer 82a ... GaN buffer layer 86 ... n-type GaN current confinement layer 92 ... undoped GaN guide layer 94 ... p-type GaN guide layer 95 ... p-type AlGaN current injection (cladding) layer 98 ... n-type InGaN (Light confinement) layer 99 ... SiO ₂ mask

Continuation of the front page (56) Reference JP-A-8-32113 (JP, A) JP-A-9-92883 (JP, A) JP-A-8-148718 (JP, A) JP-A-5-243613 (JP , A) JP 8-213651 (JP, A) JP 2-275682 (JP, A) JP 10-135575 (JP, A) JP 10-154829 (JP, A) JP 10-242514 (JP, A) JP-A-10-247745 (JP, A) JP-A-10-247761 (JP, A) JP-A-10-247760 (JP, A) JP-A-9-321389 (JP, A) A) JP-A-10-223542 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50 H01L 21/205

Claims (6)

(57) [Claims] 1. A step of forming a compound semiconductor layer having at least n-type conductivity and containing nitrogen as a constituent element on a substrate by metalorganic vapor phase epitaxy, and nitrogen having p-type conductivity as a constituent element. And a step of forming a compound semiconductor layer containing nitrogen as a constituent element having p-type conductivity. ,
At least p-type dopant raw material and ammonia (NH
₃ ) the raw material gas containing CO, and the concentration of CO and CO ₂ are 0.1 to 0.1
A method of manufacturing a nitride semiconductor device, characterized in that a carrier gas made of an inert gas purified to a range of 10 vol ppb is used. 2. The step of forming a compound semiconductor layer having p-type conduction and containing nitrogen as a constituent element comprises a group V source and III
The supply amount (mol) ratio (V / III ratio) of the group raw material is
In case of, 3000 or less, in case of GaAlN, 3600 or less
Under production method for a nitride semiconductor device according to claim 1, wherein the case of InGaN performed in 30000 the following conditions. 3. A compound semiconductor layer having p-type conductivity and containing nitrogen as a constituent element is formed as an outermost surface layer of a multilayer structure for a device, and after the step of forming the outermost surface layer having p-type conduction, The supply of the organometallic raw material for film formation is stopped, and p
Type dopant material and a predetermined time substantially inert carrier gas, or supplied at a predetermined temperature, or supplied in the cooling process
The method for manufacturing a nitride-based semiconductor device according to claim 1, wherein 4. A laminated structure of a compound semiconductor layer having at least n-type conductivity and containing nitrogen as a constituent element, a compound semiconductor layer having p-type conductivity and containing nitrogen as a constituent element, and an electrode on a substrate. In the method for manufacturing a nitride-based semiconductor device, at least the p-type dopant raw material, ammonia (NH ₃ )
A compound semiconductor layer containing p-type impurity-added nitrogen as a constituent element is formed as an outermost surface layer of a device multi-layer structure by using a source gas and a carrier gas containing after the formation to process, to stop the supply of the organic metal raw material for film formation, p-type dopant material, and the carrier gas a predetermined time, or supplied at a predetermined temperature, or wherein the supply with cooling process Manufacturing method of nitride semiconductor device. 5. The p-type dopant material is an organic magnesium (Mg) compound .
4. The method for manufacturing a nitride-based semiconductor device according to any one of 4 above. 6. The predetermined time is 30 seconds or more and less than 1 hour, the predetermined temperature is 300 ° C. or higher and the growth temperature or lower, and the temperature lowering process is the natural time within the predetermined time and predetermined temperature range. 5. The method for manufacturing a nitride-based semiconductor device according to claim 3, wherein the temperature is lowered and the slope is lowered.