JPH0529653A - Semiconductor device - Google Patents

Abstract

PURPOSE:To decrease the dislocation or distortion due to lattice mismatch by growing a GaXAl1-X-YINYN layer of a sphalerite structure on an MgF2 substrate. CONSTITUTION:An n-Ga0.7Al0.3N layer 72 is grown on an MgF2 substrate 71, and a P-Ga0.7Al0.3N layer is grown on the layer 72. This crystal growth is performed by heating the substrate. After the substrate temperature is decreased, gas is switched from H2 to NH3, and crystal growth is continued using an organometallic Ca compound, such as Ca(CH3)3. Simultaneously, aluminum and indium are introduced using an organometallic Al compound, such as Al(CH3)3, and an organometallic In compound, such as In(CH3)3. The LED thus fabricated involves a lattice mismatch and a deviation of surface orientation within + or -5%. Therefore, dislocation or distortion due to lattice mismatch is considerably decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device such as a light emitting device (hereinafter abbreviated as LED) in a short wavelength region and a semiconductor laser.

[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 light emitting device. The biggest problem is that there is no good substrate that is lattice-matched to form a short wavelength light emitting device. Therefore, various methods have been tried to reduce the influence of lattice mismatch. When the vapor phase epitaxial growth method (VPE method) is used as the crystal growth method, since the growth rate is relatively high, it is attempted to relax the strain at the interface with the substrate by growing a thick film of about 100 μm. However, it was not possible to grow a good quality crystal due to cracking. Further, in the case of the metal organic chemical vapor deposition method (MOCVD method), the growth rate was slow, and it was impossible to alleviate defects by thick film growth. For convenience,
Although it often grows on a sapphire substrate having a large lattice mismatch of about 15%, a good quality crystal cannot be obtained, and the background carrier concentration shows a very high value of 10 ¹⁹ cm ^-3 or more. Therefore, when growing on a sapphire substrate, amorphous AlN is first grown and then GaN is grown, or the substrate surface is preliminarily NH ₃
Therefore, a method of nitriding and then growing is adopted. By growing the AlN buffer layer, the carrier concentration during undoping can be reduced to about 10 ¹⁷ cm ⁻³ as compared with the case where the buffer layer is not used. However, the value is still insufficient for realization of a practical device, and although it is reported that a p-type layer was obtained by performing electron beam irradiation, it has a very high resistance, and it has an insulating property on the substrate. Since sapphire, which is the body, is used, there are limits in terms of the electrode manufacturing process and the applicable range.

[0003]

As described above, when GaN is grown and formed, a lattice defect occurs due to the absence of a substrate that is lattice-matched with GaN, and the control of the conductivity type is insufficient. There is a problem such as.

The present invention is a G having a low defect and controllable conductivity type.
The purpose is to obtain a high brightness short wavelength light emitting device by growing aN.

[0005]

[Means for Solving the Problems] In order to achieve perfect lattice matching, it was considered important not only to match the lattice constants but also to have the same lattice type. However, according to the research conducted by the present inventors, it has been found that the lattice types do not have to be the same in order to perform the lattice matching, and it is important that the distances between the lattices are the same. Further, it was found that the growth layer is affected by the substrate, and even if the crystal is originally a hexagonal crystal, the cubic crystal is adopted when the cubic crystal is lattice-matched with the substrate.

First, an example in which lattice matching can be achieved by growing hexagonal GaN on a cubic crystal or on an example MnO substrate obtained by cutting the cubic crystal in an appropriate direction will be described below. . MnO has a cubic NaCl structure and a lattice constant of 4.445. (11
1) The interstitial distance of the above two-dimensional lattice is 3.143, which is very close to the lattice constant of GaN, 3.16. Therefore, by growing GaN on the (111) plane of the MnO substrate, it becomes possible to mitigate the effect of lattice mismatch between the substrate and the growth layer. Furthermore, since AlN has a lattice constant of 3.104, it is possible to reduce the lattice constant by adding Al to GaN and to make the lattice match with the (111) plane of the MnO substrate. If the lattice matching becomes possible, dislocations and strains caused by the lattice mismatch are drastically reduced, and it becomes possible to grow a low-defect GaN crystal. When low-defect crystals can be grown, it becomes possible to obtain a low-resistance p-type crystal by increasing the activation rate of the dopant that concentrates around the defects and does not work effectively, and by performing doping. Further, AlN has a smaller lattice constant and a wider bandgap than GaN, and InN has a larger lattice constant and a narrower bandgap than GaN.
By adding an appropriate amount of Al and In, the band cap can be changed while maintaining the lattice constant, and an element having a desired emission wavelength can be obtained. Further, MnO, which is a semiconductor, is effective in the electrode manufacturing process, which has been a problem because the sapphire substrate used conventionally is an insulator.

Therefore, GaN, which is originally a hexagonal crystal, is grown on tetragonal MgF _{2 which} is lattice-matched with the substrate by adopting a cubic crystal, or on a surface obtained by cutting this in an appropriate direction. This enables stable growth.

If the lattice matching becomes possible, dislocations and strains caused by the lattice mismatch are drastically reduced, and Ga having a low defect is produced.
It becomes possible to grow N crystal. When growth is possible in a low-defect crystal, it becomes possible to obtain a p-type crystal having a low resistance by increasing the activation rate of the dopant that concentrates around the defect and does not work effectively, and by doping. In addition, AlN has a smaller lattice constant and a wider bandgap than GaN.
Since nN has a larger lattice constant and a narrower bandgap than GaN, by adding an appropriate amount of Al and In to GaN, it becomes possible to change the bandgap while maintaining the lattice constant, and an element having a desired emission wavelength can be obtained. It will be possible to obtain. Further, since MgF ₂ can stably obtain a high-quality bulk, it is relatively inexpensive and has no compositional variation. Further, how to clean the surface of the substrate before growth is usually a problem. In this respect as well, since the bond between Mg and F is strong, Mg and F evaporate independently from the surface, respectively. A clean surface can be obtained by heat treatment without any change.

[0009]

By, for example, growing a zinc blende type Ga _x Al _1-xy In _y N layer on a substrate of MgF ₂ or a cubic NaCl structure crystal, dislocations and strains caused by lattice mismatch are dramatically increased. And low defect Ga _x Al _1-xy In _y
It becomes possible to grow into N crystal, and it becomes possible to realize a high brightness and short wavelength light emitting device.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 First, an example in which MnO is used as a substrate for forming a vapor phase growth layer of a semiconductor device will be described.

FIG. 1 is a sectional view showing a schematic structure of an LED which is an embodiment of the present invention. N on the MnO substrate 11
—Ga ₀₇ Al ₀₃ N layer 12 (undoped or Si-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷
cm ^-3 ) is formed in a thickness of 3 μm, and p-Ga ₀₇ A is formed thereon.
l ₀₃ N layer 13 (Mg-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ c
m ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ) is formed in a thickness of 2 μm. In addition, both 14 and 15 in the figure are metal electrodes.

Next, the crystal growth method will be described.

FIG. 2 is a sectional view showing a schematic structure of a growth apparatus used for manufacturing an LED in the embodiment of the present invention. FIG. 21 shows a reaction tube (reaction furnace) made of quartz, and a raw material mixed gas is introduced into the reaction tube 21 through 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 11 is placed on the susceptor 24. The susceptor 24 is induction heated by the high frequency coil 25. The temperature of the substrate 11 is the same as that of the illustrated thermocouple 2.
6 and is controlled by another device (not shown).

First, the MnO substrate 11 is attached to the susceptor 24.
Place on top. 2.5 l of high-purity hydrogen is introduced from the gas introduction pipe 22 per minute to replace the atmosphere in the reaction pipe 21. Next, the gas exhaust port 23 is connected to a vacuum pump (rotary pump).
The inside of the reaction tube 21 is depressurized and the internal pressure is reduced to 20 to
Set in the range of 300 torr. Then gas inlet 2
H ₂ gas is introduced from ₂ and the susceptor and the substrate 11 are heated by the high frequency coil 25, and the substrate temperature is 500 to 1000 ° C.
Hold for 30 minutes to clean the substrate.

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. , An organometallic Ga compound such as Ga (C
Growth is carried out by introducing H ₃ ) ₃ or Ga (C ₂ H ₅ ) ₃ . At the same time, organometallic Al compounds such as Al (CH ₃ ) ₃
Alternatively, Al (C ₂ H ₅ ) ₃ and an organometallic In compound such as In (CH ₃ ) ₃ or In (C ₂ H ₅ ) ₃ are 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, a Si hydride such as SiH ₄ or an organometallic Si compound such as Si (CH ₃ ) ₄ or Se for n-type is used.
Hydrides such as H ₂ Se or organometallic Se compounds Se (CH ₃ ) ₂ , for p-type organometallic Mg compounds such as Cp ₂ Mg or organometallic Zn compounds such as Z
n (CH ₃ ) ₂ or the like is used.

[0017] Specifically, in the LED manufacturing shown in FIG. 1, NH ₃ to 1 × 10 as a starting material ^{- 3} mol / min,
Ga (C ₂ H ₅ ) ₃ at 1 × 10 ⁻⁵ mol / min, Al
(CH ₃ ) ₃ was introduced at 1 × 10 ⁻⁶ mol / min for growth. Substrate temperature is 1150 ° C, pressure is 220 torr,
The total flow rate of the raw material gas was set to 1 l / min. As the dopant, Si was used for the n-type and Mg was used for the p-type. Si was doped with silane (SiH ₄ ) and Mg was doped by mixing cyclopentadienyl magnesium (Cp ₂ Mg) into the source gas.

(Embodiment 2) FIG. 3 shows an LE according to this embodiment.
A state in which the D chip 31 is embedded in a resin case 32 that also serves as a lens is shown. Reference numeral 33 is an internal lead, and 34 is an external lead.

The LED according to this example was embedded in a resin case and a blue light emission of about 5 mcd was confirmed. No significant change was observed in this effect within the range of ± 0.5% of the lattice mismatch with the substrate. In addition, no significant change was observed within the range of ± 0.5% deviation of the plane orientation of the (111) substrate.

In this embodiment, the example using the n-type substrate is shown, but the same operation can be performed using the p-type substrate. It is also possible to add In to GaAlN to change the band gap while maintaining the lattice constant.

(Embodiment 3) FIG. 4 is a diagram showing a schematic structure of an MIS type LED which is another embodiment of the present invention. M
The n-Ga ₀₇ Al ₀₃ N layer 42 (undoped or Si-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^{−3) is formed} on the nO substrate 11.
For example, 1 × 10 ¹⁷ cm ⁻³ ) is formed in a thickness of 3 μm, and the high resistance portion 43 is formed in a part thereof. In the drawing, 44 and 45 are metal electrodes.

(Embodiment 4) FIG. 5 is a schematic diagram of a semiconductor laser device according to another embodiment of the present invention. The n-GaAlN buffer layer 52, the n-GaAl on the MnO substrate 11
N cladding layer 53, undoped GaAlN active layer 54,
A p-clad layer 55 is formed, on which n-GaAl is formed.
An N current blocking layer 56 and a p-GaAlN contact layer 57 are formed. 58 and 59 in the figure are both metal electrodes.

(Embodiment 5) FIG. 6 is a diagram showing a schematic structure of a bipolar transistor which is another embodiment of the present invention. An undoped GaAlN buffer layer 62, an n-GaAlN collector layer 63, a p-GaAl on the MnO substrate 11.
N base layer 64, n-GaAlN emitter layer 65, n-
A GaAlN emitter contact layer 66 is formed. 67, 68, and 69 in the figure are all electrodes.

An example of using MgF ₂ as a substrate for forming a vapor phase growth layer of a semiconductor device according to the present invention will be described below.

(Embodiment 6) FIG. 7 is a schematic configuration diagram of an LED which is an embodiment of the present invention. On the MgF ₂ substrate 71, an n-Ga ₀₇ Al ₀₃ N layer 72 (undoped or Si-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 × 10 6).
¹⁷ cm ^-3 ) is formed to 3 μm, and p-Ga ₀₇ Al is formed on it.
₀₃ N73 (Mg-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ⁻³
For example, 1 × 10 ¹⁷ cm ⁻³ ) is formed with a thickness of 2 μm.
In the figure, 74 and 75 are both metal electrodes.

Next, the crystal growth method described above will be described.

FIG. 8 is a schematic diagram showing a growth apparatus used in the method of the present invention. In the figure, 21 is a quartz reaction tube (reaction furnace), and a raw material mixed gas is introduced into the reaction tube 21 through a gas inlet 22. The gas in the reaction tube 21 is exhausted from the gas exhaust port 23. A carbon susceptor 2 is provided in the reaction tube 21.
4 is arranged, and the sample substrate 71 is the susceptor 24.
Placed on top. The susceptor 24 is a high frequency coil 25.
It is supposed to be heated by induction. The substrate 7
The temperature of 1 is measured by the thermocouple 26 shown and controlled by another device (not shown).

First, the MgF ₂ substrate 71 is attached to the susceptor 2
Place on top of 4. 2.5 l of high-purity hydrogen is introduced from the gas introduction pipe 22 per minute to replace the atmosphere in the reaction pipe 21. Next, the glass exhaust port 23 is connected to a mechanical (rotary) pump, the pressure inside the reaction tube 21 is reduced, and the internal pressure is set to 20 to 30.
Set in the range of 0 torr. After that, H ₂ gas is introduced from the gas introduction port 22, the susceptor 24 and the substrate 71 are heated by the high frequency coil 25, and the substrate temperature is 500 to 1000 ° C.
Hold for 30 minutes to clean the substrate.

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. , An organometallic Ga compound such as Ga (C
Growth is carried out by introducing H ₃ ) ₃ or Ga (C ₂ H ₅ ) ₃ . At the same time, organometallic Al compounds such as Al (CH ₃ ) ₃
Alternatively, Al (C ₂ H ₅ ) ₃ and an organometallic In compound such as In (CH ₃ ) ₃ or In (C ₂ H ₅ ) ₃ are 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, a Si hydride such as SiH ₄ or an organometallic Si compound such as Si (CH ₃ ) ₄ or Se for n-type is used.
Hydrides such as H ₂ Se or organometallic Se (C
H ₃ ) ₂ , for p-type organometallic Mg compounds such as Cp
₂ Mg or organometallic Zn compound such as Zn (C
H ₃ ) ₂ etc. are used.

Specifically, in manufacturing the LED of FIG. 1, NH ₃ is used as a raw material at 1 × 10 ⁻³ mol / min and Ga (C ₂
H ₅ ) ₃ was introduced at 1 × 10 ⁻⁵ mol / min, and Al (CH ₃ ) ₃ was introduced at 1 × 10 ⁻⁶ mol / min to perform growth. The substrate temperature was 1150 ° C., the pressure was 220 torr, and the total flow rate of the source gas was 1 l / min. As the dopant, Si was used for the n-type and Mg was used for the p-type. Si is silane (SiH ₄ )
, Mg is cyclopentadienyl magnesium (Cp ₂
Mg) was mixed in the source gas to dope.

(Embodiment 7) FIG. 9 shows LE according to this embodiment.
A state in which the D chip 81 is embedded in a resin case 82 that also serves as a lens is shown. Reference numeral 83 is an internal lead, and 84 is an external lead.

The LED according to this example was embedded in a resin case and a blue light emission of about 5 mcd was confirmed. No significant change was observed in this effect within the range of ± 0.5% of the lattice mismatch with the substrate. Further, no significant change was observed within the range of the plane orientation deviation of the substrate of ± 5%.

It is also possible to add In to GaAlN to change the band gap while maintaining the lattice constant.

(Embodiment 8) FIG. 10 is a schematic configuration diagram of an MIS type LED which is another embodiment of the present invention. MgF ₂
An n-Ga ₀₇ Al ₀₃ N layer 92 (undoped or Si-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ) having a thickness of 3 μm is formed on the substrate 71, and a high film is formed on a part thereof. The resistance portion 93 is formed. 9 in the figure
Both 4 and 95 are metal electrodes.

(Embodiment 9) FIG. 11 is a sectional view showing a schematic structure of a semiconductor laser device according to another embodiment of the present invention. N-GaAlN buffer layer 1 on MgF ₂ substrate 71
02, n-GaAlN cladding layer 103, undoped G
An aAlN active layer 104 and a p-clad layer 105 are formed, and an n-GaAlN current blocking layer 106 and a p-G layer are formed thereon.
The aAlN contact layer 107 is formed. In addition,
Both 108 and 109 in the figure are metal electrodes.

(Embodiment 10) FIG. 12 is a sectional view showing a schematic structure of a bipolar transistor which is another embodiment of the present invention. Undoped GaAl on the MgF ₂ substrate 71
N buffer layer 112, n-GaAlN collector layer 11
3, a p-GaAlN base layer 114, an n-GaAlN emitter layer 115, and an n-GaAlN emitter contact layer 116 are formed. Note that 117 and 118 in the figure
Are electrodes.

(Embodiment 11) FIG. 13 is a sectional view showing a schematic structure of an LED which is another embodiment of the present invention. An n-Ga ₀₇ Al ₀₃ N layer 12 is formed on a MgF ₂ substrate (not shown).
1 (undoped or Si-doped, 1 × 10 ¹⁶ to 1 ×
10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ) is formed to a thickness of 3 μm, and the p-Ga ₀₇ Al ₀₃ N layer 122 (Mg-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 ×) is formed thereon. 10 ¹⁷
cm ^-3 ) was formed to a thickness of 2 μm, and then MgF ₂ as a substrate was removed by etching. Mg
F ₂ can be etched with water, and by removing the substrate, a more efficient device can be obtained.

Further, by BP which is expected as a material for an environment-resistant elements were sphalerite lattice constant is close to the length of one side of the square surface MgF _2, the use of MgF ₂ as a substrate for BP Is also effective. At this time,
It is more effective to mix a small amount of As to achieve lattice matching.

In addition, the present invention can be variously modified and implemented without departing from the spirit thereof.

[0040]

In the past, it was thought that it was important not only to match the lattice constants but also to have the same lattice type for perfect lattice matching. It is important that the distances between the lattices are the same. In addition, it was clarified that the growth layer is affected by the substrate, and even if the crystal is originally a hexagonal crystal, the cubic crystal may be adopted when it is lattice-matched with the substrate. Due to the above, dislocations and strains caused by lattice mismatch are drastically reduced, and low defect Ga _x Al _1-xy In _y N crystals can be grown to realize a high-luminance short-wavelength light emitting device. There is a remarkable effect such as.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of an LED according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of a growth apparatus according to an embodiment of the present invention.

FIG. 3 is a sectional view of an LED in which an LED chip according to an embodiment of the present invention is embedded in a resin case.

FIG. 4 is a sectional view showing a schematic configuration diagram of an LED of an embodiment according to the present invention.

FIG. 5 is a sectional view showing a schematic configuration diagram of a semiconductor laser of an example according to the present invention.

FIG. 6 is a sectional view showing a schematic configuration diagram of a bipolar transistor of an example according to the present invention.

FIG. 7 is a sectional view showing a schematic configuration diagram of an LED of an embodiment according to the present invention.

FIG. 8 is a sectional view showing a schematic configuration of a growth apparatus according to an example of the present invention.

FIG. 9 is a cross-sectional view of an LED in which an LED chip according to an embodiment of the present invention is embedded in a resin case.

FIG. 10 is a sectional view showing a schematic configuration of an LED of an example according to the present invention.

FIG. 11 is a sectional view showing a schematic configuration diagram of a semiconductor laser of an example according to the present invention.

FIG. 12 is a sectional view showing a schematic configuration diagram of a bipolar transistor of an example according to the present invention.

FIG. 13 is a sectional view showing a schematic configuration diagram of an LED of an example according to the present invention.

[Explanation of symbols]

11 ... MnO substrate 12, 42 ... n-Ga ₀₇ Al ₀₃ N 13 ... p-Ga ₀₇ Al ₀₃ N 21 ... Reaction tube 24 ... Susceptor 31, 81 ... LED chip 32, 82 ... Resin case 33, 83 ... Internal lead 34 , 84 ... External lead 43 ... High resistance GaAlN 71 ... MgF ₂ substrate

Claims (2)

[Claims] 1. A semiconductor comprising a cubic substrate other than a group III element, and a group III-V compound semiconductor layer formed on the substrate and matched with the substrate only in a crystal lattice distance. element. 2. The semiconductor device according to claim 1, wherein the substrate is either MgF _{2 or} a cubic NaCl structure crystal.