JPH0864869A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE: To provide a semiconductor light emitting element having a small interelectrode resistance and high luminous efficiency by increasing carrier concentration and decreasing contact resistance of a semiconductor layer with an electrode metal. CONSTITUTION: A semiconductor light emitting element comprises gallium nitride compound semiconductor layers 4, 6 having at least n-type layer and a p-type layer laminated on a substrate 1, and n-type side and p-type side electrodes 9, 8 connected to the semiconductor layers of the n-type layer and the p-type layer. Accordingly, two or more types of Be, Mn, or Mg, Zn, Cd, Be and Mn are used as the dopant of the p-type layer, and two or more types of Se, S, Ge, Te, or Si, Ge, Sn, S, Se and Te are used as the dopant of the n-type layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device. More specifically, it relates to a semiconductor light emitting device using a gallium nitride based compound semiconductor suitable for blue light emission.

Here, a gallium nitride compound semiconductor is a compound of a group III element Ga and a group V element N or
A semiconductor made of a compound in which a part of Ga of the group III element is replaced with another group III element such as Al and In and / or a part of N of the group V element is replaced with another group V element such as P and As. Say.

A semiconductor light emitting device is a light emitting diode (hereinafter referred to as LED) having a double heterojunction such as a pn junction or a pin, a super luminescent diode (SLD) or a semiconductor laser diode (LD).
A semiconductor element that emits light.

[0004]

2. Description of the Related Art Conventionally, blue LEDs have a lower brightness than red and green and are difficult to put into practical use. In recent years, however, gallium nitride compound semiconductors have been used, and a low resistance p-type semiconductor layer doped with Mg has been formed. As a result, the brightness is improved and it is in the limelight.

L of a conventional gallium nitride-based compound semiconductor
The ED is manufactured by the following steps, and a perspective view of the completed gallium nitride based compound semiconductor is shown in FIG.
Shown in

First, a substrate 21 made of sapphire (Al ₂ O ₃ single crystal) or the like is used at a low temperature of 400 to 700 ° C. at a low temperature of 400 to 700 ° C. with a carrier gas H ₂ together with a carrier gas H ₂ by an organometallic compound vapor phase growth method (hereinafter referred to as MOCVD method). Trimethylgallium (hereinafter referred to as TMG) which is a gas, ammonia (NH ₃ ) and SiH ₄ as a dopant are supplied to form a low temperature buffer layer 22 composed of an n-type GaN layer, and then a high temperature of 700 to 1200 ° C. Then, the same gas is supplied to form the high temperature buffer layer 23 made of n-type GaN having the same composition.

Then, a raw material gas of trimethylaluminum (hereinafter referred to as TMA) is further added to the above gas, and n
N _- type Al _x Ga _1-x N containing Si as a type dopant
A (0 <x <1) layer is formed to form an n-type clad layer 24 for forming a double heterojunction.

Next, a material having a bandgap energy smaller than that of the clad layer, for example, trimethylindium (hereinafter TM
I) is introduced, and Ga _y In _1-y N (0 <y ≦ 1)
An active layer 25 made of is formed.

Further, biscyclopentadienyl magnesium for Mg or Zn as a p-type impurity (hereinafter referred to as "gas" used as the gas for forming the n-type cladding layer 24) is used instead of SiH _{4 as the} impurity source gas. , Cp ₂ Mg
Or dimethyl zinc (hereinafter referred to as DMZn)
Is added to the reaction tube, and the p-type cladding layer 26 of p
A type Al _x Ga _1-x N layer is vapor-grown. This makes n
The type clad layer 24, the active layer 25, and the p-type clad layer 26 form a double heterojunction.

Next, to form the cap layer 27, a gas similar to that used for the buffer layer 23 is used as an impurity source gas, ie, C.
P ₂ Mg or DMZn is supplied to grow a p-type GaN layer.

After that, a protective film such as SiO ₂ is provided on the entire surface of the growth layer of the semiconductor layer, and the temperature is 400-800 ° C. and 20-6.
Annealing is performed for about 0 minutes to activate the p-type cladding layer 26 and the cap layer 27.

After removing the protective film, a resist is applied and patterned to form an n-side electrode, and a part of each grown semiconductor layer is removed by dry etching to form an n-type GaN layer. A certain buffer layer 23 is exposed. Then, a metal film made of Pt, Ni, Au, or the like is formed by sputtering or the like to form the p-side electrode 29.
In addition, a metal film made of Al or the like is formed by the same method to form the n-side electrode 30 and is diced.
It forms an ED chip.

Next, in order to make ohmic contact between the electrode metal such as Al and the gallium nitride based compound semiconductor, heat treatment is performed at about 300 ° C. in an H ₂ atmosphere to form an alloy.

[0014]

In a conventional semiconductor light emitting device using a gallium nitride based compound semiconductor, Mg or Zn is used as a p-type dopant and S is used as an n-type dopant.
i is used, but these dopants are Ga
Since it is easily dissolved in N, the carrier concentration cannot be increased beyond a certain level. Further, when annealing is performed, the dopants are likely to move, diffuse each other and lose the steepness of the pn junction, the position of the pn junction is displaced, the operating voltage becomes high, carriers leak from the light emitting part and become a reactive current. However, there is a problem that the luminous efficiency is reduced.

Further, as an electrode, Pt is conventionally used on the p-side,
Ni, Au, etc. are used, but they are hard to react with p-type dopant Mg, and Al, etc. are used on the n-side, but they are also hard to react with n-type dopant Si. However, there is a problem that the contact resistance between the electrode metal and the semiconductor layer increases, the operating voltage of the light emitting element increases, and the light emission efficiency decreases.

An object of the present invention is to solve the above problems and to provide a semiconductor light emitting device which has a high carrier concentration and operates at a low operating voltage.

Another object of the present invention is to prevent gallium nitride-based compound semiconductors from leaking carriers without causing the pn junction to move or sag even when a heat treatment such as annealing is performed, and to obtain stable light emission characteristics. Another object of the present invention is to provide a semiconductor light emitting device comprising.

Still another object of the present invention is to reduce the contact resistance between the electrode metal and the semiconductor layer to reduce the operating voltage.
It is an object of the present invention to provide a semiconductor light emitting device capable of improving light emitting efficiency.

[0019]

As a result of extensive studies, the present inventor has conducted extensive studies in order to reduce the resistance between the p-side electrode and the n-side electrode as much as possible and reduce the reactive current to improve the luminous efficiency. By selecting the type dopant and the n-type dopant, the carrier concentration can be increased and the resistance loss can be reduced, and the sag of the pn junction can be prevented to reduce the reactive current, thereby improving the light emission efficiency. I found that I could do it. Furthermore, they have found that the contact resistance between the electrode and the semiconductor material can be reduced by using an alloy material containing a dopant of the semiconductor layer with which the electrode material is in contact, and have completed the present invention.

In the semiconductor light emitting device according to any one of claims 1 to 6, a gallium nitride based compound semiconductor layer having at least an n-type layer and a p-type layer is laminated on a substrate, and the gallium nitride based compound semiconductor of the n-type layer. A semiconductor light-emitting device comprising an n-side electrode connected to a layer and a p-side electrode connected to the gallium nitride based compound semiconductor layer of the p-type layer, wherein Various dopants are selected. In the invention of claim 1, the dopant of the p-type layer is Be, in the invention of claim 2, the dopant of the p-type layer is Mn, and in claim 3 In the invention, the dopant of the n-type layer is Se or S, and in the invention of claim 4, the dopant of the n-type layer is one element selected from the group consisting of Ge, Te and Sn. Invention of , The dopant of the p-type layer is M
At least two elements selected from the group consisting of g, Zn, Cd, Be and Mn are mixed, and in the invention of claim 6, the dopant of the n-type layer is S.
At least two elements selected from the group consisting of i, Ge, Sn, S, Se and Te are mixed.

According to a seventh aspect of the present invention, a gallium nitride-based compound semiconductor layer having at least an n-type layer and a p-type layer is laminated on a substrate, and the n-type layer and the p-type layer are gallium nitride-based compound semiconductor layers. A semiconductor light emitting device comprising n-side and p-side electrodes respectively connected to a compound semiconductor layer, wherein the n-side and / or p-side electrodes are of an n-type layer and a p-type layer to which they are respectively connected. It is an alloy containing at least one element of the dopant of the gallium nitride based compound semiconductor layer.

[0022]

According to the first aspect of the present invention, since Be is used as the p-type dopant, Be can be doped at a high concentration with an element lighter than Mg. As a result, the carrier concentration can be increased and the interelectrode resistance can be reduced.

According to the second aspect of the invention, since Mn is used as the p-type dopant, Mn is an element heavier than Mg, so it is difficult to move even by heat treatment such as annealing, and the pn junction does not move due to diffusion. , The pn junction has little sagging.

According to the third aspect of the present invention, since Se or S is used as the n-type dopant, Se or S is a group VI element, and enters the position of the N atom of the GaN-based n-type dopant. Work as. As a result, the doping can be performed at a higher concentration, the carrier concentration can be increased, and the inter-electrode resistance can be reduced.

According to the fourth aspect of the invention, since Ge, Sn or Te is used as the n-type dopant, these elements are heavier than Si and difficult to move by heat treatment such as annealing, and the pn junction is diffused. Move,
There is not much sagging. In particular, Te is a group VI element and is heavier than S and Se, so that the carrier concentration of claim 3 can be increased and deviation of the pn junction can be prevented.

According to the invention of claim 5 or 6, p
Since at least two kinds of elements are each doped as a n-type dopant or a n-type dopant, the characteristics of each dopant can be combined, and high-performance gallium nitride having high carrier concentration and preventing deviation of pn junction can be obtained. A light emitting device made of a compound semiconductor is obtained.

According to the invention of claim 7, at least one dopant of the gallium nitride based compound semiconductor layers of the n-type layer and the p-type layer, which is connected to the n-side and / or p-side electrodes, respectively, is used. Since the alloy containing the element is used, since the electrode and the gallium nitride-based compound semiconductor layer have the same element, the electrode material and the semiconductor layer are easily alloyed and the contact resistance can be reduced.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor light emitting device of the present invention will be described below with reference to the accompanying drawings.

Example 1 FIG. 1 is a process cross-sectional explanatory view of an example of a semiconductor light emitting device of the present invention.

[0030] First, as shown in FIG. 1 (a), by installing a substrate 1 made of sapphire into the reaction tube, the TMG with of H ₂ carrier gas 150 sccm, NH
₃ 10000 sccm, and SiH ₄ concentration diluted with H ₂ is 100ppm as a dopant to 10sccm introduced, the low temperature buffer layer 2 and the high-temperature buffer layer composed of a gallium nitride based compound semiconductor layer, such as for example n-type GaN by MOCVD 3 is 0.01 to 0.
It grows about 2 μm, 2 to 5 μm.

After that, 1 more TMA is added to the above-mentioned gas.
N-type Al _x Ga _1-x added at a flow rate of 0 to 100 sccm
The n-type clad layer 4 made of N (0 <x <1) is 0.1 to
After growth of 0.3 μm, SiH ₄ is stopped, TMI is introduced at a flow rate of 50 to 200 sccm instead of TMA, and the active layer 5 made of non-doped Ga _y In _{1 -y} N having a smaller bandgap energy than the cladding layer 4 is introduced. To 0.05
It grows to a thickness of ˜0.1 μm.

Further, with the same source gas as the source gas used for forming the n-type cladding layer 4, the impurity source gas was replaced with SiH ₄ and Be as a p-type impurity was replaced with bismethylcyclopentadienylberyllium (hereinafter referred to as (MeCp ₂ ) Be) gas is added to the reaction tube at about 10 to 1000 sccm, and the impurity concentration of B is about 10 ¹⁷ to 10 ¹⁹ / cm ^3.
A p-type cladding layer 6 made of e-containing Al _x Ga _1-x N is vapor-phase grown to a thickness of 0.1 to 0.3 μm.

Then, for forming the cap layer 7, SiH is used as an impurity source gas with the same gas as the above-mentioned buffer layer 3.
P-type GaN by supplying (MeCp) ₂ Be instead of ₄
The layer is grown about 0.3-2 μm.

After that, a protective film such as SiO ₂ is provided on the entire surface of the growth layer of the semiconductor layer, and the temperature is 400-800 ° C. and 20-6.
Annealing is performed for about 0 minutes to activate the p-type cladding layer 6 and the cap layer 7.

Next, in order to form the n-side electrode after removing the protective film, a resist is applied and patterned, and a part of each grown semiconductor layer is removed by dry etching to form an n-type GaN layer. The buffer layer 3 is exposed. Then, a metal film made of Au, Al, or the like is formed by sputtering or the like, and the p-side electrode 8 electrically connected to the p-type layer on the surface of the stacked compound semiconductor layers, the exposed surface of the high temperature buffer layer 3 are formed. By forming an n-side electrode 9 electrically connected to the n-type layer by dicing and
The ED chip is completed.

According to the present embodiment, 3.0 V was conventionally required to pass a current of 20 mA, but an applied voltage of 2.8 to 2.9 V was sufficient, and power consumption was reduced.

Example 2 In this example, in the semiconductor light emitting device of Example 1, the dopant for the p-type cladding layer 6 and the cap layer 7 was replaced with Be, and M was added.
n is used, and other structures are the same as those in the first embodiment.

The p-type cladding layer 6 and the cap layer 7 are formed using the dopant gas of Example 1 (MeCp) _2.
Instead of Be, Mn was introduced into the reaction tube as bismethylcyclopentadienyl manganese (hereinafter, referred to as (MeCp) ₂ Mn) gas at about 10 to 1000 sccm, and the Mn content was about 10 ¹⁷ to 10 ¹⁹ / cm ^3. Al _x G
The p-type clad layer 6 made of a1 _-xN (0 <x <1) is vapor-phase grown to a thickness of about 0.1 to 0.3 μm, and the other manufacturing method is the same as that of the first embodiment.

According to this example, it can be seen that, after annealing, the originally undoped layer has a small change in carrier concentration due to diffusion and no pn junction movement occurs.

Example 3 In this example, Se or S was used instead of Si as the n-type dopant of the n-type cladding layer 4 and the buffer layers 2 and 3 of Example 1, and the other structures were the same as those of Example 1. The same as 1. When Se or S is used as a dopant, hydrogen selenide (H ₂ Se) gas or H _{2 respectively}
Dilute it with H ₂ as S gas, add a gas with a concentration of 100 ppm to about 1 to 100 sccm, and introduce it into the reaction tube.
Buffer layers 2 and 3 composed of N layers and n-type cladding layer 4
The n-type Al _x Ga _1-x N (0 <x <1) layer is vapor-grown so that the impurity concentration becomes about 10 ¹⁷ to 10 ¹⁹ / cm ³ .

Further, p-type Al _x Ga _1-x N (0 <x <
As the dopant of the p-type cladding layer 6 which is the layer 1) and the cap layer 7 which is the p-type GaN layer, the same Mg as the conventional one was used, but Be or Mn used in Example 1 or 2 may be used.

According to the present embodiment in which Mg is used as the p-type dopant and Se or S is used as the n-type dopant, the current of 20 mA is the same as that of the conventional semiconductor light emitting device using Si as the impurity of the n-type cladding layer 4. Conventionally, 3.0 V was required to obtain a current, but an applied voltage of 2.8 to 2.9 V was sufficient, and lower power consumption than that in the past was obtained.

Example 4 In this example, Ge, Sn or Te is used in place of the n-type impurity Se or S in the semiconductor light emitting device of Example 3, and other structures are the same as in Example 3. is there. Dopant Ge, Sn, the doping of Te, the concentration 100ppm of monogermane with H ₂ dilution, respectively (G
eH ₄ ) gas, tin hydride (SnH ₄ ) gas, hydrogen telluride (TeH ₄ ) gas of about 1 to 100 sccm was added to the reaction tube, and the impurity concentration of the n-type cladding layer 4 was changed as in Example 3. N-type A of about 10 ¹⁷ to 10 ¹⁹ / cm ³
An l _x Ga _1-x N (0 ≦ x <1) layer is vapor-grown.

As in the third embodiment, the p-type Al _x Ga _{1 -x} N layer which is the p-type cladding layer 6 and the cap layer 7 may be replaced by Be or Mn instead of Mg.

Example 5 In this example, the dopant of the p-type cladding layer 6 of the semiconductor light emitting device of Example 1 was replaced with Be, and Mg, Zn, Cd, B were used.
At least two kinds of metals are used among e and Mn, and other structures are the same as those in the first embodiment.

For example, for Be and Mn, the respective dopant source gases are (MeCp) ₂ Be for 10 to 1000 sc.
cm, (MeCp) ₂ Mn is introduced at 10 to 1000 sccm for vapor phase growth, and under certain conditions, Be and Mn are doped in the semiconductor layer in the same amount, and the impurity concentration is 1
A p-type clad layer 6 made of Al _x Ga _1-x N (0 ≦ x <1) doped with Be and Mn of about 0 ¹⁷ to 10 ¹⁹ / cm ³ is vapor-phase grown.

In this embodiment, since at least two kinds of impurity source gas for the p-type cladding layer 6 are introduced, the carrier concentration is higher and the pn junction has a steepness than in the case of one kind of impurity source gas. Therefore, it is particularly effective for a semiconductor light emitting device having a pn junction.

Example 6 In this example, Si, Ge, Sn, S, and n are used as n-type dopants of the n-type cladding layer 4 of the semiconductor light emitting device of Example 3.
At least two elements of Se or Te are used, and the other structures are the same as in Example 3. In order to dope the dopants Si, Ge, Sn, S, Se, Te, the concentration is 100 ppm when diluted with H _2.
SiH ₄ gas, GeH ₄ gas, SnH ₄ gas, H ₂ S
Gas, H ₂ Se gas, and TeH ₄ gas may be introduced into the reaction tube during vapor phase growth of the semiconductor layer. At least two kinds of these gases, for example, S and Te, are selected and the flow rate is about 10 sccm and 10 sccm, respectively. Then, the high temperature buffer layer 3 made of n-type GaN and the n _- type cladding layer 4 made of n _- type Al _x Ga _{1 -x} N are vapor-deposited.

According to this embodiment, the buffer layer is made of the low-resistance dopant S, and the cladding layer is made of the dopant Te by using p.
The n-junction was difficult to move and the luminous efficiency was increased.

As in Example 3, the p-type Al _x Ga _{1 -x} N layer, which is the p-type clad layer 6, is used as a dopant in Examples 1, 2 or 5 instead of the conventional Mg. It may be the one that you had.

Example 7 In this example, at least one of the n-side electrode 9 and the p-side electrode 8 (see FIG. 1 (d)) of the semiconductor light emitting device is a chip of the n-type layer and the p-type layer to which they are respectively connected. The alloy is characterized by being an alloy containing a dopant element of the gallium nitride-based compound semiconductor layer.

For example, Mg as a p-type layer dopant
, The alloy of Mg and Au cannot be formed, and the electrode is A
Although it is unavoidable to use u, Ti, Ni, Pt, etc. in combination, it is possible to make an alloy of Zn and Au by mixing Zn with Mg as a dopant.
It is easy to make ohmic contact with the semiconductor layer.

[0053]

According to the semiconductor light emitting device of the present invention, since the carrier concentration can be made high by selecting the dopant of the gallium nitride based compound semiconductor, the resistance becomes low, and the voltage is lower than the conventional one and the same as the conventional one. It can emit light with brightness. That is, high brightness can be obtained by applying the same voltage as the conventional one.

Further, by making the dopant an element heavier than Mg or Si, the junction position of the pn junction becomes difficult to move, and a highly reliable LED or LD whose emission position is stable is provided.
It is possible to obtain a semiconductor light emitting device such as.

Furthermore, the electrode material and the dopant can be combined, the contact resistance between the n-type layer or the p-type layer and the electrode metal can be reduced, and a semiconductor light emitting device with improved luminous efficiency can be obtained. .

[Brief description of drawings]

FIG. 1 is a process sectional view showing an example of a method for manufacturing a semiconductor light emitting device of the present invention.

FIG. 2 is a perspective view showing an example of a conventional semiconductor light emitting device.

[Explanation of symbols]

 1 substrate 2 low temperature buffer layer 3 high temperature buffer layer 4 n-type clad layer 5 active layer 6 p-type clad layer 7 cap layer 8 p-side electrode 9 n-side electrode

Claims (7)

[Claims] 1. A gallium nitride based compound semiconductor layer having at least an n-type layer and a p-type layer is laminated on a substrate,
A semiconductor light emitting device comprising an n-side electrode connected to the gallium nitride-based compound semiconductor layer of the n-type layer and a p-side electrode connected to the gallium nitride-based compound semiconductor layer of the p-type layer, respectively. A semiconductor light emitting device in which the dopant of the gallium nitride based compound semiconductor layer of the p-type layer is Be. 2. A gallium nitride based compound semiconductor layer having at least an n-type layer and a p-type layer is laminated on a substrate,
A semiconductor light emitting device comprising an n-side electrode connected to the gallium nitride-based compound semiconductor layer of the n-type layer and a p-side electrode connected to the gallium nitride-based compound semiconductor layer of the p-type layer, respectively. A semiconductor light emitting device in which the dopant of the gallium nitride based compound semiconductor layer of the p-type layer is Mn. 3. A gallium nitride-based compound semiconductor layer having at least an n-type layer and a p-type layer is laminated on a substrate,
A semiconductor light emitting device comprising an n-side electrode connected to the gallium nitride-based compound semiconductor layer of the n-type layer and a p-side electrode connected to the gallium nitride-based compound semiconductor layer of the p-type layer, respectively. A semiconductor light emitting device in which the dopant of the gallium nitride based compound semiconductor layer of the n-type layer is Se or S. 4. A gallium nitride-based compound semiconductor layer having at least an n-type layer and a p-type layer is laminated on a substrate,
A semiconductor light emitting device comprising an n-side electrode connected to the gallium nitride-based compound semiconductor layer of the n-type layer and a p-side electrode connected to the gallium nitride-based compound semiconductor layer of the p-type layer, respectively. A semiconductor light emitting device, wherein the dopant of the gallium nitride based compound semiconductor layer of the n-type layer is one element selected from the group consisting of Ge, Te and Sn. 5. A gallium nitride based compound semiconductor layer having at least an n-type layer and a p-type layer is laminated on a substrate,
A semiconductor light emitting device comprising an n-side electrode connected to the gallium nitride-based compound semiconductor layer of the n-type layer and a p-side electrode connected to the gallium nitride-based compound semiconductor layer of the p-type layer, respectively. The dopant of the gallium nitride based compound semiconductor layer of the p-type layer is Mg, Zn, C
A semiconductor light emitting device in which at least two elements selected from the group consisting of d, Be and Mn are mixed. 6. A gallium nitride based compound semiconductor layer having at least an n-type layer and a p-type layer is laminated on a substrate,
A semiconductor light emitting device comprising an n-side electrode connected to the gallium nitride-based compound semiconductor layer of the n-type layer and a p-side electrode connected to the gallium nitride-based compound semiconductor layer of the p-type layer, respectively. The dopant for the gallium nitride based compound semiconductor layer of the n-type layer is Si, Ge, S
A semiconductor light emitting device in which at least two elements selected from the group consisting of n, S, Se and Te are mixed. 7. A gallium nitride-based compound semiconductor layer having at least an n-type layer and a p-type layer is laminated on a substrate,
A semiconductor light emitting device comprising an n-side electrode connected to the gallium nitride-based compound semiconductor layer of the n-type layer and a p-side electrode connected to the gallium nitride-based compound semiconductor layer of the p-type layer, respectively. The material of the n-side and / or p-side electrode is an alloy containing at least one element of the dopants of the gallium nitride-based compound semiconductor layers of the n-type layer and the p-type layer to which they are respectively connected. Semiconductor light emitting device.