JP3522610B2 - Method for manufacturing p-type nitride semiconductor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a p-type nitride semiconductor among GaN group III nitride semiconductors used in a light emitting device or the like that emits short-wavelength light such as blue light, and particularly to an annealing treatment after growth. The present invention relates to a method for manufacturing a p-type nitride semiconductor that does not require

[0002]

2. Description of the Related Art In recent years, a GaN group III nitride semiconductor having a relatively large band gap has been attracting attention as a material for a light emitting element having a short wavelength used in an optical information processing apparatus and the like, which has an increasing amount of information. It is indispensable for the light emitting elements such as the diode element and the laser element to have a pn junction that recombines carriers near the junction surface and emits the recombined light. As is well known, p doped with an acceptor such as magnesium (Mg)
Since the activation rate of magnesium in the type nitride semiconductor is significantly lower than that of the donor, it is not easy to obtain a p-type nitride semiconductor having low resistance.

Therefore, in the past, heat treatment (post-annealing) was performed on a p-type nitride semiconductor, which had a high resistance even after returning to room temperature after growth, so that hydrogen in a composite of magnesium and hydrogen was converted from magnesium. A method of obtaining a low resistance p-type nitride semiconductor by dissociation is generally performed. However, in order to improve the productivity, research is underway to obtain a low-resistance p-type nitride semiconductor without performing post-annealing.

The conventional p-type disclosed in Japanese Patent Laid-Open No. 10-135575, which does not require post-annealing, is described below.
A method of manufacturing the type nitride semiconductor will be described.

This publication describes metal organic vapor phase epitaxy (MOV).
PE) on the substrate made of sapphire
A group III source such as G, a nitrogen source such as ammonia, and an organomagnesium compound containing a p-type dopant are introduced as a carrier gas of nitrogen gas containing hydrogen gas at a concentration of 0.8% to 20% by volume, and the substrate temperature is At 1100 ° C. for growing a p-type nitride semiconductor. As a result, the formation of a complex of magnesium and hydrogen is blocked, and a p-type nitride semiconductor having low resistance during growth is obtained. Furthermore, in the cooling process, about 3
350 in a nitrogen gas atmosphere containing 2% by volume of ammonia
Disclosed is a method of lowering the temperature to 0 ° C. and then stopping the introduction of ammonia to lower the temperature to room temperature.

[0006]

However, the conventional method for manufacturing a p-type nitride semiconductor that does not perform post-annealing has the following problems. That is, the paper (Applied Phys
ics Letters, vol.72, (1998), p.1748), the hydrogen concentration in the crystal growth step is 2.4% to 3.
Even if it is increased to 7%, the activation of magnesium is significantly inferior, and a p-type nitride semiconductor cannot be obtained at the time of growth unless it is grown at a very low hydrogen concentration. Moreover, when a p-type nitride semiconductor is grown at a low hydrogen concentration, surface migration becomes insufficient, so that predetermined atoms are not arranged at optimum positions on the surface, and a good crystal cannot be obtained.

An object of the present invention is to solve the above-mentioned conventional problems and to obtain a good quality p-type nitride semiconductor without performing post-annealing.

[0008]

In order to achieve the above-mentioned object, the present invention provides a method for manufacturing a p-type nitride semiconductor, in which a low-resistance p-type nitride semiconductor is formed in a growth step, and a cooling step is performed. By controlling the cooling time or the atmosphere, the low resistance is maintained within a practical range as a p-type semiconductor.

Specifically, the p-type nitride semiconductor manufacturing method according to the present invention is performed in an atmosphere containing hydrogen at a capacity ratio of 5% to 70%.
A semiconductor in which a p-type nitride semiconductor layer is formed on a substrate by introducing a p-type dopant source, a nitrogen source, and a group III source onto the substrate held at a substrate temperature of 600 ° C. or higher in air. The p-type nitride semiconductor layer grown in a high temperature state includes a layer forming step and a cooling step of cooling the substrate on which the p-type nitride semiconductor layer is formed.
A method of manufacturing a p-type nitride semiconductor in which the carrier concentration in the p-type nitride semiconductor at room temperature is reduced by cooling time for cooling to 00 ° C., wherein a substrate in a high temperature state in which a p-type nitride semiconductor layer is formed is used. Regarding the relationship between the cooling time for cooling to 600 ° C. and the carrier concentration in the p-type nitride semiconductor layer at room temperature, the carrier concentration in the p-type nitride semiconductor layer at room temperature changes from the high temperature state assumed from the above relationship. 6
The cooling time is set within 5 minutes so that 60% or more of the carrier concentration in the p-type nitride semiconductor layer at room temperature when the cooling time for cooling to 00 ° C. is 0 minutes is present.

According to the p-type nitride semiconductor manufacturing method of the present invention, a low-resistance p-type nitride semiconductor layer is formed on a substrate in an atmosphere containing hydrogen to the extent that the inactivation of the p-type dopant can be suppressed. In addition, the hole carrier concentration of the p-type nitride semiconductor layer is reduced to such an extent that its low resistance can be maintained .
Because, without performing post annealing, it is possible to obtain a p-type nitride semiconductor having excellent crystal quality.

In the p-type nitride semiconductor manufacturing method according to the present invention, it is preferable that the reduction rate of the hole carrier concentration in the p-type nitride semiconductor layer is about 0% to 95% in the cooling step. By doing so, for example, assuming that the hole carrier concentration immediately after growth is about 2.0 × 10 ¹⁷ cm ⁻³ , even if the hole carrier concentration is reduced by 95%, 1.0 × 10 ¹⁶ c
Since a concentration of about m ⁻³ is secured, a p-type nitride semiconductor that can withstand practical use can be obtained.

In the p-type nitride semiconductor manufacturing method according to the present invention, in the cooling step, the substrate temperature is about 60 ° C. from the growth temperature.
It is preferable to include a step of cooling to 0 ° C. within 30 minutes. By so doing, it is possible to reliably maintain the low resistance of the hole carrier concentration of the p-type nitride semiconductor layer that is practically useable.

In the p-type nitride semiconductor manufacturing method according to the present invention, it is preferable that the atmosphere in the semiconductor layer forming step contains hydrogen in a capacity ratio of about 5% to 70%. Generally, when an organometallic material is used as a group III source or p-type dopant, hydrogen is included in the atmosphere in order to enhance the decomposition efficiency of these and to promote surface migration. However, when the hydrogen concentration to be added exceeds 70%, the inactivation (passivation) of the acceptor due to hydrogen becomes remarkable. Therefore, when the hydrogen concentration is about 5% to 70% as in the present invention, the p-type dopant is Inactivation can be surely suppressed.

[0014]

[0015]

[0016]

In the p-type nitride semiconductor manufacturing method according to the present invention , in the cooling step, the substrate temperature is about 60 from the growth temperature.
In the atmosphere while the temperature drops to 0 ° C, the capacity ratio is 0% to 50%.
It is preferable to contain hydrogen of about%. By doing so, passivation of hydrogen in the p-type nitride semiconductor layer can be suppressed, so that the low resistance of the hole carrier concentration of the p-type nitride semiconductor layer can be reliably maintained.

In the p-type nitride semiconductor manufacturing method according to the present invention , the substrate temperature is about 60 ° C. from the growth temperature in the cooling step.
It is preferable to include ammonia in the atmosphere while the temperature is lowered to 0 ° C. By doing so, desorption of nitrogen from the surface of the grown p-type nitride semiconductor is suppressed, and thus deterioration of the surface can be prevented.

[0019]

The p-type nitride semiconductor according to the present invention is intended for a p-type nitride semiconductor formed on a substrate at a growth temperature higher than 600 ° C., and the hole carrier concentration immediately after cooling is the growth temperature. 5% to 100 of the hole carrier concentration in
%.

According to the p-type nitride semiconductor of the present invention, when the hole carrier concentration immediately after growth is about 2.0 × 10 ¹⁷ cm ⁻³ , the hole carrier concentration immediately after cooling is 5% immediately after growth.
Even if it becomes, a concentration of about 1.0 × 10 ¹⁶ cm ⁻³ is secured, so that it becomes a p-type nitride semiconductor that can sufficiently withstand practical use.

Another p-type nitride semiconductor according to the present invention is intended for a p-type nitride semiconductor sequentially formed on a substrate at a growth temperature higher than 600 ° C., and the p-type nitride semiconductor has an upper surface. Is exposed and the hydrogen concentration near the upper surface of the p-type nitride semiconductor is equal to or less than about 10 times the hydrogen concentration inside the p-type nitride semiconductor.

In the case of the p-type nitride semiconductor obtained by the conventional method of performing post-annealing, the hydrogen concentration near the exposed upper surface is 10 times or more higher than the hydrogen concentration inside the p-type nitride semiconductor. However, according to the p-type nitride semiconductor of the present invention, the hydrogen concentration near the upper surface of the p-type nitride semiconductor is equal to or less than about 10 times the hydrogen concentration inside the p-type nitride semiconductor. The p-type nitride semiconductor has an improved activation rate of the type dopant.

[0024]

Embodiment 1 Embodiment 1 of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a p-type nitride semiconductor according to the first embodiment of the present invention. As shown in FIG. 1, on a substrate 11 made of sapphire, a buffer layer 12 made of gallium nitride (GaN) and relaxing a lattice mismatch between a desired semiconductor grown on the substrate 11 and sapphire. P-type nitride semiconductor layer 13 made of GaN
And are sequentially formed.

A method of manufacturing the p-type nitride semiconductor layer having the above structure will be described below. First, the substrate 11 having a mirror-like main surface is held in a substrate holder in a reaction tube (not shown), and then the temperature of the substrate 11 is set to about 1000 ° C. while introducing hydrogen gas onto the substrate 11, 11 to about 10
By heating for a minute, dirt and moisture such as organic substances attached to the main surface of the substrate 11 are removed.

Next, the temperature of the substrate 11 is lowered to about 550 ° C., nitrogen gas having a flow rate of about 16 L / min as carrier gas and ammonia (NH ₃ ) gas as a nitrogen source having a flow rate of about 4 L / min. And a flow rate of about 40 μmol / min III
Substrate 1 with trimethylgallium (TMG) as a group source
Introduced on the substrate 1, the buffer layer 12 made of GaN with a thickness of 25 nm is grown on the main surface of the substrate 11.

Next, after temporarily stopping the supply of TMG to the reaction tube and raising the substrate temperature to about 1050 ° C., the nitrogen gas flow rate is about 13 L / min and the hydrogen gas flow rate is about 3 L / min. As a carrier gas, a flow rate of about 4 L / min of ammonia gas, a flow rate of about 80 μmol / min of TMG, and a flow rate of about 0.2 μmol / min of biscyclopentadienyl magnesium containing magnesium as a p-type dopant ( Cp ₂ Mg) is introduced onto the substrate 11 for about 60 minutes to grow the p-type nitride semiconductor layer 13 made of Mg-doped GaN having a thickness of 2 μm on the buffer layer 12. The hydrogen gas flow rate referred to here includes hydrogen gas for vaporizing TMG and Cp ₂ Mg.

Next, after the supply of TMG and Cp ₂ Mg to the reaction tube was stopped, the flow rate of the atmospheric gas was about 13 L.
The substrate 11 is cooled from the growth temperature to room temperature while introducing nitrogen gas / minute, hydrogen gas having a flow rate of about 3 L / minute, and ammonia gas having a flow rate of about 4 L / minute onto the substrate 11. After cooling, the substrate 11 on which the p-type nitride semiconductor layer 13 is formed is taken out from the reaction tube.

The features of the cooling method of the present invention for the substrate 11 on which the p-type nitride semiconductor layer 13 is formed will be described below.

FIG. 2 is a graph showing the cooling time dependency on the hole carrier concentration in the cooling step of the method for manufacturing the p-type nitride semiconductor according to the first embodiment of the present invention. here,
As the cooling time for lowering the substrate temperature from around 1050 ° C. of the growth temperature to 600 ° C., the hole carrier concentration of the p-type nitride semiconductor layer 13 was measured by dividing it into 5 types from 5 minutes to 40 minutes. is doing. The hole carrier concentration is
As a sample for five kinds of measurement, a chip of 5 mm square is cut out from the substrate 11, and the Hall effect of each cut chip is measured.

As shown in FIG. 2, the conductivity type of each of the five types of samples is p-type.
It can be seen that the hole carrier concentration decreases as the cooling time to ℃ becomes longer. By extrapolating the straight line shown in FIG. 2 as a y-intercept where the cooling time is 0 minutes, the p-type nitride semiconductor layer 13 according to the present embodiment has a hole carrier concentration of about 2 × immediately after growth. It can be said to exhibit a p-type conductivity of 10 ¹⁷ cm ^-3 .

Further, as shown in FIG. 2, the hole carrier concentration when the cooling time is 5 minutes is 1.2 × 10 ¹⁷ cm ^−3, and the hole carrier concentration when the cooling time is 20 minutes is It shows 3.0 × 10 ¹⁶ cm ⁻³ corresponding to about 7% of the concentration before cooling, and 1.0 × 10 ¹⁶ cm ⁻³ corresponding to 5% of the concentration before cooling when the cooling time is 30 minutes. Indicates. When the cooling time is 30 minutes, it is close to the lower limit of the p-type layer used for the device. Furthermore, when the cooling time is 40 minutes, the concentration is 2.
It shows 2 × 10 ¹⁵ cm ⁻³ , which is an insufficient carrier concentration for the device.

(First Modification of First Embodiment) Hereinafter, the first modification will be described.
A method for manufacturing the p-type nitride semiconductor layer according to the first modification of the embodiment will be described.

First, as shown in FIG. 1, the buffer layer 12 on the substrate 11 and the p-type nitridation having a hole carrier concentration of about 2 × 10 ¹⁷ cm ⁻³ are formed by the same method as in the first embodiment. The semiconductor layer 13 is sequentially formed.

Next, the dependence of the hole carrier concentration on the hydrogen gas concentration in the atmosphere gas in the cooling step according to the first modification will be described. Here, the hole carrier concentration is measured by dividing the hydrogen gas concentration in the atmosphere gas into four types of 0%, 30%, 50% and 70%. In either case, the concentration of ammonia gas in the atmosphere is about 20%.
And the rest is nitrogen gas. The substrate temperature is lowered from about 1050 ° C to about 600 ° C, which is a growth temperature, to about 5 ° C.
Cooling in minutes.

The measurement results are shown below.

1) In an atmosphere having a hydrogen concentration of 0%, about 2 × 10 ¹⁷ cm ^{−3, which} is the same value as immediately after growth, 2) In an atmosphere having a hydrogen concentration of 30%, 4.2 × 10 ¹⁶ cm ⁻³ 3. ) In an atmosphere with a hydrogen concentration of 50%, it is about 5% immediately after growth, about 1 × 10 ¹⁶ cm ^-3 4) In an atmosphere with a hydrogen concentration of 70%, it is about 1% immediately after growth. 5 × 10 ¹⁵ cm ⁻³ As described above, when cooling is performed in an atmosphere having a hydrogen concentration of 70%, even if the temperature is lowered to 600 ° C. for 5 minutes, the p-type layer used in the device is insufficient.

(Second Modification of First Embodiment) A method for manufacturing a p-type nitride semiconductor layer according to the second modification of the first embodiment will be described below.

First, as shown in FIG. 1, the buffer layer 12 on the substrate 11 and the p-type nitridation having a hole carrier concentration of about 2 × 10 ¹⁷ cm ⁻³ are formed by the same method as in the first embodiment. The semiconductor layer 13 is sequentially formed.

Next, the dependence of the hole carrier concentration on the ammonia gas concentration in the atmosphere gas in the cooling step of the second modification will be described. The hydrogen gas concentration in the atmosphere is about 15%, and the rest is nitrogen gas. The substrate temperature is lowered from the growth temperature of about 1050 ° C. to 600 ° C. in about 5 minutes.

As a result of the measurement, it has been confirmed that even if the ammonia gas concentration is changed, the reduction rate of the hole carrier concentration in the cooling step is almost the same as that when the ammonia gas concentration is 20%. Note that when the ammonia gas concentration is in the range of 0% to 0.5%, the p-type nitride semiconductor layer 13 is
The desorption of nitrogen from the surface of the Al deteriorates the crystallinity.

(Third Modification of First Embodiment) A method of manufacturing a p-type nitride semiconductor layer according to a third modification of the first embodiment will be described below. In this modification, the dependence of the hole carrier concentration on the hydrogen gas concentration in the carrier gas in the step of forming the p-type nitride semiconductor layer 13 shown in FIG. 1 will be described. In the first embodiment, the concentration of hydrogen gas in the carrier gas is about 15%. In this modification,
The concentration of hydrogen gas in the carrier gas is 5% in 5% increments from 0% to 20%, and the range from 20% to 80% is 1
There are 6 types for each 0% and a total of 11 types.
When the hydrogen gas concentration is 0%, TMG and Cp ₂
Mg is vaporized using nitrogen gas.

As a result of the measurement, the hydrogen gas concentration is 5% to 70%.
In the p-type nitride semiconductor layer 13 grown in a certain range, similarly to FIG. 2, the value obtained by extrapolation with the cooling time being 0 minute is 1 × each as the hole carrier concentration immediately after the growth. It is 10 ¹⁶ cm ⁻³ or more, indicating a p-type. More specifically, the hydrogen gas concentration is 5% to 50%.
%, The hole carrier concentration is about 5 × 10 ¹⁶ cm ^-3
As described above, when the hydrogen gas concentration is about 10% to 20%, the hole carrier concentration is about 1 × 10 ¹⁷ cm ⁻³ or more.
Above all, when the hydrogen gas concentration was grown to 15%,
Immediately after the growth, the hole carrier concentration becomes highest, and the value is 2 × 10 ¹⁷ cm ⁻³ .

On the other hand, the full width at half maximum of the rocking curve by X-ray diffraction, which is a measure of crystallinity, becomes smaller as the hydrogen gas concentration increases, and the full width at half maximum shows 300 seconds or less when the hydrogen gas concentration is 10% or more. However, the hydrogen gas concentration is 0
%, The full width at half maximum of the rocking curve by X-ray diffraction is 500 seconds, and the crystallinity is significantly deteriorated.
Further, the high resistance makes it impossible to measure the hole carrier concentration.

Similarly, when the hydrogen gas concentration is grown to about 80%, the resistance is high and the hole carrier concentration cannot be measured. It is considered that this is because the amount of hydrogen atoms taken into the GaN crystal during the growth increased and the activation rate of magnesium decreased.

In this embodiment, ammonia is used as the nitrogen source, but for example, hydrazine (N
Any organic nitrogen raw material such as ₂ H ₄ ) or ethyl azide (C ₂ H ₅ NH ₂ ) may be used.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a sectional view showing the structure of a nitride semiconductor light emitting device according to the second embodiment of the present invention. As shown in FIG. 3, the epitaxial layer of the nitride semiconductor light emitting device according to the second embodiment includes a substrate 21 made of sapphire.
A buffer layer 22 made of non-doped GaN, and
An n-type contact layer 23 made of GaN doped with silicon (Si), a light emitting layer 24 made of non-doped InGaN, a first cladding layer 25 made of non-doped GaN, and p made of AlGaN doped with magnesium. The second type cladding layer 26 and the p-type contact layer 27 made of magnesium-doped GaN are sequentially laminated. p-type contact layer 27
A translucent p-side electrode 28 is formed on the top of which nickel (Ni) and gold (Au) are laminated in this order.
An n-side electrode 29 made of aluminum (Al) is formed on the exposed region of the n-type contact layer 23. As described above, the present light emitting device includes the n-type contact layer 2 with the non-doped light emitting layer 24 and the first cladding layer 25 interposed.
3 is a light emitting diode element having a pn junction between the second cladding layer 26 and the second cladding layer 26.

Hereinafter, a method of manufacturing the light emitting diode element having the above structure will be described.

First, the substrate 21 having a mirror-like main surface is held in a substrate holder inside a reaction tube (not shown), and then the temperature of the substrate 21 is set to about 1000 ° C. and hydrogen gas is introduced onto the substrate 21. Meanwhile, the substrate 21 is heated for about 10 minutes. As a result, dirt and water such as organic substances attached to the main surface of the substrate 21 are removed to obtain a clean surface.

Next, the temperature of the substrate 21 is lowered to about 550 ° C., nitrogen gas having a flow rate of about 16 L / min as carrier gas, and ammonia gas as a nitrogen source having a flow rate of about 4 L / min are flown at a flow rate of about 4 L / min. By introducing about 40 μmol / min of TMG as a group III source onto the substrate 21, the substrate 2
A buffer layer 22 having a thickness of 25 nm and made of GaN is grown on the main surface of 1. Here, the flow rate of the hydrogen gas contained in the carrier gas also includes the hydrogen gas used for vaporizing TMG or Cp ₂ Mg.

Next, after temporarily stopping the supply of TMG to the reaction tube and raising the substrate temperature to about 1050 ° C., the nitrogen gas flow rate is about 13 L / min and the hydrogen gas flow rate is about 3 L / min. As a carrier gas, an ammonia gas with a flow rate of about 4 L / min, TMG with a flow rate of about 80 μmol / min, and 10 ppm monosilane (SiH ₄ ) gas containing silicon as an n-type dopant at a flow rate of about 10 cc / min. Of the buffer layer 2 on the substrate 21 for about 60 minutes.
An n-type contact layer 23 having a thickness of 2 μm and made of Si-doped GaN is grown on the substrate 2.

Next, after stopping the supply of TMG and SiH ₄ gas, the substrate temperature is lowered to about 750 ° C. At this growth temperature, nitrogen gas having a flow rate of about 14 L / min and ammonia gas having a flow rate of about 6 L / min as carrier gases,
TMG flow rate is about 4 μmol / min and flow rate is about 5 μmo
trimethyl indium (T
(MI) is introduced onto the substrate 21 to grow a light emitting layer 24 having a single quantum well structure made of InGaN and having a thickness of 3 nm on the n-type contact layer 23. In this case, the In composition of the light emitting layer 24 is about 0.2.

Next, after stopping the supply of TMI, nitrogen gas as a carrier gas, ammonia gas as a nitrogen source and TMG as a group III source are introduced into the substrate 21 at the same flow rates until the substrate temperature reaches about 1050.degree. Until the temperature is raised, the first cladding layer 25 made of GaN having a thickness of 10 nm is grown on the light emitting layer 24.

Next, after the substrate temperature reaches about 1050 ° C., the flow rate of nitrogen gas is about 13 L / min and the flow rate is about 3 L / min.
Minute hydrogen gas as a carrier gas, the flow rate is about 4 L / min ammonia gas, and the flow rate is about 40 μmol / min TMG.
And another group III source trimethylaluminum (TMA) with a flow rate of about 6 μmol / min and a flow rate of about 0.1 μm
By introducing ol / min of Cp ₂ Mg onto the substrate 21, the second cladding layer 26 made of Mg-doped p-type AlGaN having a thickness of 0.2 μm is formed on the first cladding layer 25. Grow.

Next, after the supply of TMA was stopped, the substrate temperature was kept at about 1050 ° C., the nitrogen gas flow rate was about 13 L / min, and the hydrogen gas flow rate was about 3 L / min. About 4 L / min of ammonia gas and a flow rate of about 8
TMG of 0 μmol / min and flow rate of about 0.2 μmol / min
By introducing Cp ₂ Mg of the amount on the substrate 21,
On the second cladding layer 26, a p-type contact layer 27 made of p-type GaN having a thickness of 0.3 μm and doped with Mg.
Grow.

Next, after forming the p-type contact layer 27, nitrogen gas having a flow rate of about 13 L / min, hydrogen gas having a flow rate of about 3 L / min, and ammonia gas having a flow rate of about 4 L / min are used as atmosphere gases. While the substrate temperature is being introduced into the reaction tube, the substrate temperature is cooled from the growth temperature to room temperature, and the substrate 21 on which the stacked body (epitaxial layer) including the plurality of nitride semiconductor layers is formed is taken out from the reaction tube. At this time, the hydrogen gas concentration in the atmosphere gas is about 15%, and the ammonia gas concentration is about 20%. Here, the cooling time for cooling the substrate 21 from the growth temperature of about 1050 ° C. to 600 ° C. is set to 5 minutes.

The nitride semiconductor layer thus obtained, in particular, the p-type second cladding layer 26 and the p-type contact layer 27 are formed by the same growth method and cooling method as in the first embodiment. ing. Therefore, a p-type semiconductor layer having low resistance and good quality is formed without performing post-annealing for activating the magnesium doped in the second cladding layer 26 and the p-type contact layer 27.

Next, a silicon oxide film is deposited on the p-type contact layer 27 by using, for example, the CVD method, and then,
The deposited silicon oxide film is patterned into a predetermined shape by photolithography to form a mask pattern for etching made of the silicon oxide film. Then, using this mask pattern, reactive ion etching is performed on the epitaxial layer until the n-type contact layer 23 is exposed.

Next, using the vapor deposition method, for example, the exposed n
The n-side electrode 29 is selectively formed on the p-type contact layer 23, and similarly, the p-side electrode 28 is formed on the p-type contact layer 27.
Are selectively formed.

Next, the surface (back surface) of the substrate 21 opposite to the epitaxial layer is polished until the thickness of the substrate 21 becomes about 100 μm, and separated into chips by scribing. The separated individual chips are fixed to the stem having electrodes with the element formation surface side facing upward, and then the p-side electrode 28 and the n-side electrode 29 on the chip are connected to the stem electrodes by wires. After that, the chip is sealed with resin to obtain a light emitting diode element.

When the light emitting diode element thus obtained is driven by a forward current of 20 mA,
It has been confirmed that blue light with a peak wavelength of 470 nm is output. The light emission output at this time is 2.0 mW,
The forward operating voltage is 4.0V.

(First Modification of Second Embodiment) In the cooling step according to the second embodiment, the substrate 21 having the epitaxial layer formed thereon is grown at a temperature of about 1050 ° C. to 600 ° C.
The light emitting diode element having the structure shown in FIG. 3 is formed by setting the cooling time to 25 minutes to 25 minutes. It has been confirmed that when the light emitting diode element thus formed is driven by a forward current of 20 mA, blue light having a peak wavelength of 470 nm is output. In this case, the light emission output is 0.5 mW and the forward operation voltage is 5.0V.

(Comparative Example) In the cooling step according to the present embodiment, the cooling time for cooling the substrate 21 on which the epitaxial layer is formed from the growth temperature of about 1050 ° C. to 600 ° C. is 40 minutes, and is shown in FIG. A light emitting diode element having a structure is formed. It has been confirmed that, when the light emitting diode element thus formed is driven with a forward current of 20 mA, no current flows due to high resistance and no light is emitted.

FIG. 4 is a graph showing the hydrogen distribution in the depth direction from the surface in the nitride semiconductor light emitting devices according to the second embodiment of the present invention, its first modification and comparative example.
It is a result by distribution of MS. It represents the hydrogen concentration when measured at the above three different cooling times. Here, in FIG. 4, regions corresponding to the semiconductor layers shown in FIG. 3 are denoted by the same reference numerals. Also, the growth temperature of 105
Regarding the cooling time for cooling from around 0 ° C. to 600 ° C., the curve 1A is the case of 5 minutes of the present embodiment, the curve 1B is a modification thereof of 25 minutes, and the curve 1C is the comparative example.
The case of 0 minutes is shown.

As can be seen from the curve 1A in FIG. 4, when the cooling time is 5 minutes, the hydrogen concentration near the surface is about 3.0 × 1.
0 ¹⁹ cm ⁻³ , which decreases from the surface toward the substrate (n-type contact layer 23 direction), and in the second cladding layer 26, the hydrogen concentration is approximately constant, about 1.0 × 10 5.
^It shows ¹⁹ cm ^-3 . In addition, the first cladding layer 25,
The light emitting layer 24 and the n-type contact layer 2 have detection limits of 2.
It is 0 × 10 ¹⁸ cm ⁻³ or less.

When the cooling time shown in the curve 1B according to the first modification is 25 minutes, the hydrogen concentration near the surface is about 1.0 × 1.
It can be seen that it is 0 ²⁰ cm ⁻³ , decreases from the surface toward the substrate, and the hydrogen concentration in the second cladding layer 26 is approximately constant at about 1 × 10 ¹⁹ cm ⁻³ .

The cooling time shown in the curve 1C according to the comparative example is 4
At 0 minutes, the hydrogen concentration near the surface is approximately 3.0 x 10 ^20.
cm ⁻³ , which decreases in the direction from the surface to the substrate, and the hydrogen concentration in the second cladding layer 26 is about 1 × 10 ¹⁹ cm ^−3, which is almost constant.

Further, as shown in FIG. 4, the cooling time is 25
In the case of not more than the minute, it is found that the hydrogen concentration on the upper surface of the p-type contact layer 27 is within 10 times the hydrogen concentration of the second cladding layer 26.

As described above, according to the present embodiment and the first modification thereof, the carrier gas during the growth of the p-type second cladding layer 26 and the p-type contact layer 27 contains about 5% by volume to the carrier gas. A high-quality p-type semiconductor layer having a low resistance can be obtained immediately after the growth by including about 70% by volume, preferably about 15% by volume of hydrogen gas.

Further, in the cooling step, the cooling time for cooling from the growth temperature of 600 ° C. or higher to about 600 ° C. is set within about 30 minutes, preferably about 5 minutes, and the atmosphere gas is about 50% by volume or less of hydrogen gas and By using about 0.5% by volume or more of ammonia gas, the reduction rate of the hole carrier concentration of the p-type semiconductor layer can be suppressed to about 0% to 95%. As a result, it is possible to realize a high output nitride semiconductor light emitting device at a low voltage.

[0073]

According to the method of manufacturing a p-type nitride semiconductor of the present invention, a low-resistance p-type nitride semiconductor layer is formed on a substrate in an atmosphere containing hydrogen to the extent that deactivation of the p-type dopant can be suppressed. Since the p-type nitride semiconductor layer is formed and cooled in a cooling time or atmosphere in which the hole carrier concentration of the p-type nitride semiconductor layer is reduced to such an extent that its low resistance can be maintained, post-annealing is not performed. A p-type nitride semiconductor having excellent crystal quality can be obtained.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view showing a p-type nitride semiconductor according to a first embodiment of the present invention.

FIG. 2 is a graph showing the cooling time dependency on the hole carrier concentration in the cooling step of the method for manufacturing a p-type nitride semiconductor according to the first embodiment of the present invention.

FIG. 3 is a structural cross-sectional view showing a nitride semiconductor light emitting device according to a second embodiment of the present invention.

FIG. 4 is a graph showing the hydrogen concentration distribution from the surface to the depth direction in the nitride semiconductor light emitting device according to the second embodiment of the present invention, its first modification and its comparative example.

[Explanation of symbols]

11 board 12 buffer layers 13 p-type nitride semiconductor layer 21 board 22 Buffer layer 23 n-type contact layer 24 Light-emitting layer 25 First clad layer 26 Second cladding layer 27 p-type contact layer 28 p-side electrode 29 n-side electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidemi Takeishi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-9-40490 (JP, A) JP-A-10 -313133 (JP, A) JP-A-11-238692 (JP, A) JP-A-10-135575 (JP, A) JP-A-6-326416 (JP, A) JP-A-8-325094 (JP, A) ) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01S 5/00-5/50 H01L 33/00

Claims (3)

(57) [Claims] 1. An atmosphere containing hydrogen in a volume ratio of 5% to 70%.
A p-type nitride semiconductor layer is formed on the substrate by introducing a p-type dopant source, a nitrogen source and a group III source onto the substrate which is kept at a substrate temperature higher than 600 ° C. in air. A semiconductor layer forming step and a cooling step of cooling the substrate on which the p-type nitride semiconductor layer is formed are provided, and the p-type nitride semiconductor layer grown in a high temperature state is cooled from a high temperature state to 600 ° C. The cooling time decreases the carrier concentration in the p-type nitride semiconductor at room temperature p
A method of manufacturing a p-type nitride semiconductor, comprising:
Regarding the relationship between the cooling time for cooling to ° C and the carrier concentration in the p-type nitride semiconductor layer at room temperature, the carrier concentration in the p-type nitride semiconductor layer at room temperature is 600 from the high temperature state assumed from the above relationship. The cooling time is set within 5 minutes so that 60% or more of the carrier concentration in the p-type nitride semiconductor layer at room temperature when the cooling time for cooling to 0 ° C. is 0 minutes is present. Type nitride semiconductor manufacturing method. 2. The atmosphere in the step of lowering the substrate temperature from the substrate temperature in the semiconductor layer forming step to 600 ° C. in the cooling step contains hydrogen with a capacity ratio of 0% to 50%. The method for manufacturing a p-type nitride semiconductor according to claim 1. 3. The p-type nitride semiconductor according to claim 1, wherein, in the cooling step, the atmosphere in the step of lowering the substrate temperature from the substrate temperature in the semiconductor layer forming step to 600 ° C. contains ammonia. Manufacturing method.