JPH07249796A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To realize high luminance short wave emission by adding group II and IV elements simultaneously to an emission layer 11 thereby increasing the emission center without increasing diffusion of impurities. CONSTITUTION:A GaN buffer layer 12, an n-type GaN confinement layer 13, a GaN emission layer 14 doped with Se and Mg and a P-type GaN confinement layer 15 are grown on a saphire substrate 11 and a P side electrode 16 is formed on the layer 15 while an n side electrode 17 is formed on the side face of the buffer layer 12. Since a GaxAlxIn1-x-yN layer(0<x<=1, 0<=y<1) added simultaneously with group II and Vl elements is employed as an emission layer, the impurities are taken into the crystal as a pair of doner and acceptor thus suppressing the diffusion. Consequently, lowering of efficiency or deterioration of quality due to increase of lattice defect is prevented even if a relatively large quantity of impurities is added in order to increase the number of emission centers thus realizing a high luminance short waveform LED.

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 using a compound semiconductor material, and more particularly to a semiconductor light emitting device using a GaN material.

[0002]

2. Description of the Related Art GaN, which is one of III-V group compound semiconductors containing nitrogen, has a large band gap of 3.4 eV and is a direct transition type, and is expected as a material for a short wavelength blue light emitting device. . In a semiconductor light emitting device using a GaN-based material, the light emitting layer is usually a p-type layer to which a group II acceptor impurity such as Zn or Mg is added, and light emission from a deep level (light emission center) created by the impurity is used. is doing.

In this type of semiconductor light emitting device, it is necessary to increase the number of light emitting centers in the light emitting layer in order to suppress the brightness saturation and achieve high brightness. To increase the light emitting centers, however, the light emitting layer is required. If a high concentration of impurities is doped, a large amount of impurities will diffuse from the light emitting layer during film formation. For this reason, there are problems that the luminous efficiency cannot be improved, the lattice defects increase and the quality deteriorates, and high brightness cannot be achieved.

Further, when the light emitting layer is doped with impurities at a high concentration, the wave functions of the electrons bound by the acceptors are overlapped with each other and the light emitting efficiency is drastically reduced. When light emission due to a transition with a donor impurity is used, relatively high concentration doping is possible, but this is low in efficiency because the light emission involves spatial movement of electrons.

These become particularly serious problems when trying to realize a green-blue semiconductor laser, and until now, Ga has been a problem.
An operation example of a green-blue semiconductor laser using an N-based material has not been reported.

[0006]

As described above, the conventional Ga
In a semiconductor light emitting device using an N-based material, it is necessary to increase the concentration of impurities in order to increase the number of light emission centers in order to increase the brightness. It is difficult to realize high-luminance and short-wavelength light emission because there is a problem that quality is deteriorated due to increase of lattice defects and lattice defects.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to increase the number of light emitting centers without increasing the diffusion of impurities from the light emitting layer. An object is to provide a semiconductor light emitting device that can realize light emission.

[0008]

In order to solve the above problems, the present invention employs the following configurations. That is, the present invention _{is, Ga x Al y In 1-} xy N layer (0 <x ≦ 1,0 ≦
A semiconductor light emitting device having y <1) as a light emitting layer is characterized in that a group II element and a group VI element are simultaneously added to the light emitting layer.

The following are preferred embodiments of the present invention. (1) Ga _s Al _t In _1-st N (0 <s ≦ 1, 0 <t ≦
1) A first conductivity type cladding layer consisting of Ga _x Al _y I
n _1-xy N (0 <x ≦ 1, 0 ≦ y <1, y <t) active layer (light-emitting layer), and second conductivity type cladding layer made of Ga _s Al _t In _1-st N It has a double heterojunction structure. (2) Mg, Be, Z as group II elements added to the light emitting layer
n, Cd, or Hg is used, and as a group VI element, Se, O, S
Or use Te. (3) The concentration of the group II element and the group III element added to the light emitting layer is 5 × 10 ¹⁹ cm ⁻³ or more, preferably 1 × 1.
Set it to 0 ²⁰ cm ^-3 or higher.

[0010]

The main reason why high concentration impurities cannot be added to the light emitting layer is that the impurities diffuse from the light emitting layer. Therefore, the inventors of the present invention have conducted extensive studies and various experiments, and when an acceptor impurity and a donor impurity are added at the same time, a donor-acceptor pair (D-A pair) is formed and incorporated into a crystal. It was found that the diffusion of impurities could be dramatically suppressed. Further, according to this method, since the light emission does not utilize the defect, not only the light emission efficiency is improved, but also the yield is significantly improved. In particular,
Since Zn easily diffuses, this method is effective. Also,
Since Cd has a deep level to be created, higher brightness can be expected.

Moreover, when the group VI element is used as the donor impurity, it is particularly effective for forming a closest pair with the group II element which is the acceptor impurity. In addition,
In order to make this method more effective, the addition amount of each of the donor impurity and the acceptor impurity in the light emitting layer should be 5 ×.
10 ¹⁹ cm ⁻³ or more, preferably 1 × 10 ²⁰ cm ⁻³ or more, and the concentration difference between the donor and the acceptor is 5 × 10 ¹⁹
It is preferably cm ^-3 or less. For this purpose, it is necessary to improve the controllability of the doping amount, and it is better that the difference in vapor pressure between the added impurities is large. From this point as well, a combination of a group VI element having a high vapor pressure as a donor impurity and a group II element as an acceptor impurity is desirable. Especially II
A combination of Zn as a group element and O as a group VI element is ideal because it can be added at a higher concentration because the bond lengths of GaN and ZnO are substantially equal. Further, as the Group II element, Cd, Hg, and Be can be used in the same manner in addition to Zn, and for example, a combination of Be and S, Se, Ta can be exemplified.

As another combination of acceptor impurities and donor impurities, there is a combination of Si and C. In this case, C substitutes a group V atom to act as an acceptor, and Si substitutes a group III atom to form a donor. Work as.
Further, when adding III group B, V group As, P, etc., they do not diffuse because they are in the same group as the constituent elements, but because they form an isoelectronic trap in the crystal, pseudo D The luminous efficiency is improved as in the case of using the -A pair. Therefore, in the present invention, in addition to the group II element and the group VI element as described above, these impurities may be appropriately used in combination.

As described above, according to the present invention, the group II element and the group VI element are simultaneously added as acceptor impurities and donor impurities at the same time, so that impurity diffusion from the light emitting layer is not caused in the light emitting layer. The number of light emitting centers in a certain GaInAlN layer increases, which makes it possible to realize a semiconductor light emitting device with high brightness and short wavelength.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing an element structure of a blue LED according to a first embodiment of the present invention. A GaN buffer layer 12 having a thickness of 50 nm and an n-type GaN confinement layer 13 (Si-doped: 5 × 10 ¹⁷ cm) on a sapphire substrate 11.
^-3 , thickness 1 μm), Se and Mg doped thickness 0.5
μm GaN light emitting layer 14, p-type GaN confinement layer 15
(Mg-doped: 1 × 10 ¹⁸ cm ⁻³ , thickness 1 μm) is grown and formed. A p-side electrode 16 is formed on the confinement layer 15, and an n-side electrode 17 is formed on the side surface of the buffer layer 12.

Here, a feature of this embodiment is that Mg is added as a group II element and Se is added as a group VI element to GaN as the light emitting layer 14. Se in the light emitting layer 14
The concentrations of Mg and Mg were 1 × 10 ²⁰ cm ⁻³ , respectively. In addition to Mg, Se, Zn, Cd, Hg, etc. are used as acceptors, and Si, Ga, Sn, P are used as donors in addition to Se.
b, O, S, Te, etc. can be used. Of these, Mg or Zn is suitable for blue, Cd is suitable for green, and Hg is suitable for red.

As described above, in this embodiment, the GaN light emitting layer 1
Since Mg and Se are simultaneously added to 4, the impurities form a donor-acceptor pair (D-A pair) and are taken into the crystal, so that the diffusion of the impurities from the light emitting layer 14 is prevented. It can be dramatically reduced. Therefore, even if a relatively large amount of impurities is added in order to increase the number of light emitting centers, the efficiency is not lowered and the quality is not lowered due to the increase of lattice defects. Therefore, an LED with high brightness and short wavelength can be realized.

FIG. 2 is a schematic configuration diagram showing a growth apparatus used for manufacturing the device of this embodiment. In the figure, 21 is a reaction tube made of quartz, and a raw material mixed gas is introduced into the reaction tube 21 from a gas introduction port 22. The gas in the reaction tube 21 is exhausted from the gas exhaust port 23.

A susceptor 24 made of carbon is arranged in the reaction tube 21, and the sample substrate 27 is used as the susceptor 2.
4. The susceptor 24 is induction heated by the high frequency coil 25. The temperature of the substrate 27 is measured by the illustrated thermocouple 26 and controlled by another device.

Next, a method of manufacturing an LED using the apparatus shown in FIG. 2 will be described. First, the sample substrate 27 (sapphire substrate 11) is placed on the susceptor 24. Gas inlet 2
High-purity hydrogen from 2 is introduced at a rate of 1 l / min to replace the atmosphere in the reaction tube 21. Next, the gas exhaust port 23 is connected to a rotary pump to reduce the pressure in the reaction tube 21 and reduce the internal pressure to 2
Set in the range of 0 to 300 Torr.

Next, after lowering the substrate temperature to 450 to 900 ° C., the H ₂ gas is switched to NH ₃ gas, N ₂ H ₄ gas or an organic compound containing N, for example (CH ₃ ) ₂ N ₂ H ₂ . Together with an organometallic Ga compound, for example Ga
(CH ₃ ) ₃ or Ga (C ₂ H ₅ ) ₃ is introduced to grow. At the same time, if necessary, an organometallic Al compound such as Al (CH ₃ ) ₃ or Al (C ₂ H ₅ ) ₃ and an organometallic In compound such as In (CH ₃ ) ₃ or In (C
₂ H ₅ ) ₃ is introduced to add Al and In.

When doping is performed, a doping raw material is also introduced at the same time. As a doping raw material, Mg
For use in organometallic Mg compounds such as Mg (C ₂ H ₅ ).
_{2, Mg (C 6 H 7} ) 2, organometallic Be compound as a Be, for example, _{Be (CH 3) 2, Be} (C 2 H 5) 2,
Organometallic Zn compounds for Zn, such as Zn (CH
₃ ) ₂ , Zn (C ₂ H ₅ ) ₂ , Cd organometallic C
d compounds such as Cd (CH ₃ ) ₂ and Cd (C ₂ H ₅ ).
₂ , organometallic Hg compounds for Hg, such as Hg (C
H _{3) 2,} using a _{Hg (C 2 H 5) 2} .

For Se, Se hydride such as H ₂ Se or an organometallic Se compound such as Se (CH
₃ ) ₂ , Se (C ₂ H ₅ ) ₂ , CO ₂ for NO, NO
₂ , N ₂ O, H ₂ O, C ₃ H ₈ OH, S hydrides for S, such as H ₂ S or organometallic S compounds, such as S
_{(CH 3) 2, S (} C 2 H 5) 2, organometallic Te compound as a Te, for example, _{Te (CH 3) 2, Te} (C 2 H
₅ ) Use ₂ .

For Si, a Si hydride such as SiH ₄ or an organometallic Si compound such as Si (CH
₃ ) ₂ , Si (C ₂ H ₅ ) ₂ , Ge hydrides for Ge such as GeH ₄ or organometallic Ge compounds such as G
e (CH ₃ ) ₄ , Ge (C ₂ H ₅ ) ₄ , and Sn for organometallic Sn compounds such as Sn (CH ₃ ) ₄ and Sn (C
₂ H ₅ ) ₄ is used. Furthermore, for Pb, an organometallic Pb compound such as Pb (CH ₃ ) ₄ or Pb (C ₂ H
₅ ) Use ₄ .

Specifically, in manufacturing the LED shown in FIG. 1, NH ₃ is used as a raw material at 1 × 10 ⁻³ mol / min and Ga.
(CH ₃ ) ₃ at 1 × 10 ⁻⁵ mol / min, Al (CH ₃ ) ₃
^Is 1 × 10 ^-6 mol / min, In (CH ₃ ) ₃ is 1 × 10 ^-6
Introduce and grow at mol / min. Substrate temperature is 1000 ° C,
The pressure was 76 Torr, and the total flow rate of the raw material gas was 1 l / min. Si, Mg, Se are used as the dopant, and SiH is used as the raw material.
₄ , Cp ₂ Mg and H ₂ Se were used, respectively. (Embodiment 2) FIG. 3 is a sectional view showing an element structure of a semiconductor laser according to a second embodiment of the present invention. 3C-Si
An n-GaInAlN buffer layer 32 is formed on the C substrate 31, and an n-GaInAlN cladding layer 33,
InGaN light emitting layer 34 containing Zn and O, and p-G
A double heterojunction structure composed of the aInAlN cladding layer 35 is formed. N-GaIn having a stripe-shaped opening is formed on the cladding layer 35 of the double heterojunction structure.
An AlN current blocking layer 36 is formed and p-GaI is formed thereon.
The nAlN contact layer 37 is formed. And
A p-side electrode 38 is formed on the contact layer 37, and an n-side electrode 39 is formed on the lower surface of the substrate 11.

The light emitting layer 34 constituting the double heterojunction structure is In _0.35 Ga _0.65 N and the cladding layers 33 and 35.
Is In _0.35 Ga _0.55 Al _0.1 N. Further, in this crystal laminated structure, after growing from the buffer layer 32 to the current blocking layer 36 on the substrate 31 by the first growth, a stripe-shaped groove is formed in the current blocking layer 36, and the second growth is performed. Then, the contact layer 37 is grown and formed.

With such a structure, the emission center can be increased by adding a relatively large amount of Zn and O to InGaN, which is the light emitting layer 34. In this case, by simultaneously adding Zn and O, it is possible to suppress the diffusion of impurities from the light emitting layer 34 into the cladding layers 33 and 35. As a result, a semiconductor laser with high brightness and short wavelength can be realized.

The present invention is not limited to the above embodiments. Other Group II elements can be used in place of Zn and Mg added to the light emitting layer, and other Group VI elements can be used in place of Se and O added to the light emitting layer. Further, the element structure is not limited to those shown in FIGS. 1 and 3, and can be appropriately changed according to the specifications. In addition, various modifications can be made without departing from the scope of the present invention.

[0028]

As described in detail above, according to the present invention, the number of emission centers of the GaInAlN layer, which is the emission layer, increases.
It is possible to realize a high brightness short wavelength light emitting device and a green-blue semiconductor laser.

[Brief description of drawings]

FIG. 1 is a sectional view showing an element structure of an LED according to a first embodiment.

FIG. 2 is a schematic configuration diagram showing a growth apparatus used for manufacturing the device of the first embodiment.

FIG. 3 is a sectional view showing an element structure of a semiconductor laser according to a second embodiment.

[Explanation of symbols]

 11 ... Sapphire substrate 12 ... GaN buffer layer 13 ... n-type GaN confinement layer 14 ... GaN light-emitting layer 15 ... p-type GaN confinement layer 16, 17, 38, 39 ... Electrode 21 ... Reaction tube 22 ... Gas inlet 23 ... Gas exhaust Mouth 24 ... Susceptor 25 ... High-frequency coil 26 ... Thermocouple 27 ... Sample substrate 31 ... 3C-SiC substrate 32 ... n-GaInAlN buffer layer 33 ... n-GaInAlN cladding layer 34 ... InGaN light emitting layer 35 ... p-GaInAlN cladding layer 36 ... n-GaInAlN current blocking layer 37 ... p-GaInAlN contact layer

Claims (1)

[Claims] 1. A G to which a group II element and a group VI element are added at the same time.
_{a x Al y In 1-xy} N layer (0 <x ≦ 1,0 ≦ y <1)
A semiconductor light-emitting device characterized by using as a light-emitting layer.