JPH10256670A - Compound semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a new semiconductor laser by allowing growth of a compound thin film equivalent to a semiconductor of the compound of nitride, phosphorus, and arsenide, which is not realized so far. SOLUTION: Relating to a compound semiconductor laser wherein a plurality of semiconductor thin films of III-V based semiconductor are laminated on an n-type GaAs substrate 11, an active layer 14 among a plurality semiconductor thin films is formed of super lattice of 100nm in thickness, in combination of a GaAs layer 142 of 5.6nm for undope and a GaInN layer 142 of 0.5nm. And relating to the GaInN layer 142 part, Ga:In is designed to be 8:2 so that it is almost equal to GaAs in combination length in design.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor device, and more particularly to a compound semiconductor device using a group III-V compound semiconductor to form a light emitting diode or a semiconductor laser.

[0002]

2. Description of the Related Art In recent years, light emitting diodes (LEDs) and semiconductor lasers (LDs) using III-V compound semiconductors have been developed.
It is widely used for optical communication, multimedia related business and LED display panel. Above all, InGaAsP
Since the mixed crystal semiconductor of the system has an emission wavelength of 1.3 to 1.5 μm in a region where the transmittance of an optical fiber is high, it is extremely important as a light source for optical communication, and is a key device in the communication industry in the future. . Semiconductor lasers made of this semiconductor have achieved satisfactory performance in terms of oscillation threshold and life, but are significantly inferior to visible LDs in terms of temperature characteristics, and improved temperature characteristics are required. ing.

The key to improving the temperature characteristics is not the element structure but the material properties. This is explained by the phenomenon that the energy difference on the conduction band side of the two semiconductor layers constituting the double hetero structure is small, so that the overflow of electrons occurs and the light output is reduced. That is, it cannot be avoided due to the intrinsic properties of the material. On the other hand, recently InGaN
There is a proposal that the above overflow can be prevented by using a compound called As. However, this I
In a compound in which N is added to nGaAs, it is extremely difficult to mix N to the order of percent in composition ratio, and a compound having a desired nitrogen concentration has not been obtained.

[0004] In the field of display elements, there is a strong demand for LDs and LEDs having wavelengths from blue to green. In this regard, a light emitting device made of GaInN, which has been difficult until now, has been experimentally manufactured. The emission wavelength of this semiconductor is generally very short in the blue region, and the growth of a film having a high In composition that emits green light has been studied for use as a light source for displays. However, there is a fatal drawback that when the amount of In increases, it becomes chemically unstable in the air. On the other hand, it is easily presumed that the effect is obtained by partially adding As or P instead of N, but N is simply expressed as A
Substitution with s is almost impossible, and development of an effective method of incorporating As or P is desired.

[0005]

As described above, conventionally, Ga
Attempts to add 1% or more of N to As or GaP have been attempted by only a few research institutions, but N has achieved satisfactory results due to the large difference in atomic radius and electronegativity from P and As. Not. In recent years, N plasma sources have been developed, and 2-3% of them can be introduced. However, the adverse effect of plasma has been suggested, and application as an element has been questioned. Furthermore, considering application as an element, a high-quality single crystal thin film of 5% or more was required. Conversely, GaI
It was also difficult to partially replace As with P instead of N in a light emitting element composed of nN.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a compound having properties equivalent to those of a compound semiconductor of nitride, phosphorus and arsenide, which could not be produced conventionally. It is an object of the present invention to provide a compound semiconductor element which can grow a thin film and can be expected to be applied to a light emitting element and an electronic device which have not existed conventionally.

[0007]

[Means for Solving the Problems]

(Structure) In order to solve the above problem, the present invention employs the following structure. That is, the present invention provides a single crystal substrate
In a compound semiconductor device in which a plurality of semiconductor thin films made of a group III-V compound semiconductor are stacked, at least a part of the plurality of semiconductor thin films is formed of a first compound layer made of a group V element containing nitrogen and a group III element. And a second compound layer comprising a group V element and a group III element that do not contain nitrogen are alternately laminated, and the one of the first and second compound layers having a lattice constant farthest from the substrate is the substrate. It is characterized by being formed thinner than the one having a closer lattice constant.

Here, preferred embodiments of the present invention include the following. (1) Of the first and second compound layers, the thinner one is 5
nm or less. (2) The substrate is GaAs or InP, and the first compound layer is formed thinner than the second compound layer.

(3) The substrate is made of GaP or Si, and the second compound layer is formed thinner than the first compound layer. (4) the first compound layer is _{Al v Ga w In 1-vw} N (0 ≦
v, a w ≦ 1), the second compound layer Al _x Ga _y I
n _1-xy As _z P _1-z (0 ≦ x, y, z ≦ 1).

(5) The cycle of alternate lamination of the first and second compound layers is set to 20 nm or less. (6) The ratio of the thicknesses of the first and second compound layers is set to 1/2 or less or 2 times or more.

(7) As group III-V compounds, B, A1, G
Use a, In, N, P, As, and Sb. (Operation) As described above, the reason why N is not easily replaced with As or P is that N is significantly different from P or As in atomic radius or electronegativity, and thus cannot be essentially avoided.
Therefore, a method of generating an effect of mixing with unmixed ones can be considered. For that purpose, the concept of a superlattice is used.

In general, a mixed crystal semiconductor of A and B has properties similar to those of the superlattice semiconductor of A and B. The advantage of using a superlattice is that even a composition having a composition ratio that does not normally mix stably can be produced with a superlattice structure. In the current superlattice, only the change of the band structure due to the formation of the quantum well structure and the zone folding is considered, and the proposed superlattice is applied to the thermodynamically unstable mixed crystal semiconductor of As, P and N proposed here. Use is a new concept.

However, it is not always possible to produce a superlattice in any combination. The nitride of In, Ga, and Al has a wurtz-type crystal structure, and phosphide and arsenide have a diamond structure, and the respective crystal structures are different. Therefore, generation of crystal defects is unavoidable in a normal growth method.

By the way, in the world of thin film growth, when a thin layer having a thickness of about 10 nm or less is grown even if the crystal structure is different, the crystal structure becomes the same as the underlying crystal structure, and defects such as dislocations do not occur (pseudomorphic). Has been identified in many systems. Therefore, as long as one layer is sufficiently thin, a thin film with few defects can be grown even by a combination of different crystal structures by forming a superlattice structure. Therefore, it is possible to synthesize a compound having a composition in which the composition ratio of the nitride layer and the arsenide or phosphide is one-sided. In this case, in the combination of the structures having different composition ratios, the closer the bond length is, the more the occurrence of defects is reduced. The technique is also applicable to the case where the same type of structure has a difference in lattice constant.

As described above, in the present invention, a compound having a composition which is not mixed by the conventional method is synthesized. The realization of an unusual crystal structure is significantly different from the use of a superlattice structure for designing a band structure. According to this method,
A high-quality semiconductor thin film such as GaAs or InP incorporating the properties of nitride can be manufactured, and the effect of improving the performance of a light-emitting element or the like is extremely large.

Therefore, according to the present invention, a semiconductor thin film having the same properties as a compound obtained by mixing nitrogen into arsenide or phosphide or a compound obtained by mixing arsenic or phosphorus into nitride can be produced. When this thin film is used in a light emitting device, not only does the light emitting region become enlarged, but also in a device with a long wavelength, the energy difference between the active layer and the cladding layer on the conduction band side can be increased. It has the effect of conversion.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. (First Embodiment) FIG. 1 is a diagram showing a semiconductor laminated structure of a superlattice LD according to a first embodiment of the present invention. This is because GaAs exhibits the properties of GaInNAs on average.
An active layer formed of a superlattice of GaInN and GaInN;
This is an example of an LD wafer having a double hetero structure composed of a cladding layer of AIAs. The oscillation wavelength was designed to be around 1.3 μm due to the effect of reducing the band gap when a small amount of N was mixed into GaAs and the introduction of In.

An n-type GaAs wafer is used as a substrate 11, on which an n-type GaAs buffer layer 12 (having a thickness of 2 μm) is formed.
m and a carrier concentration of 3 × 10 ¹⁸ cm ⁻³ ),
n-type Ga _0.7 Al _0.3 As clad layer 13 (film thickness 1.5
μm, carrier concentration of 8 × 10 ¹⁷ cm ⁻³ ), active layer 14,
p-type Ga _0.7 AI _0.3 As clad layer 15 (film thickness 2.5
μm, carrier concentration 1 × 10 ¹⁸ cm ⁻³ ), p-type GaAs
Layer contact layer 16 (thickness 0.3 μm, carrier concentration 3
× 10 ¹⁸ cm ^-3 ) was sequentially grown.

The active layer 14 is a combination of an undoped 5.6 nm GaAs layer 141 and a 0.5 nm GaInN layer 142, and is formed of a 100 nm thick superlattice.
The GaInN layer 142 has a Ga: In ratio of 8: 2 and G
It was designed so that the bond length was almost equal to aAs. This is effective for suppressing defects in the superlattice portion.

Each semiconductor layer was grown by MOCVD (metal organic chemical vapor deposition). In raw material is trimethylindium (TMI), and Ga raw material is triethylgallium (TMI).
EGa) and Al raw materials are trimethyl aluminum (TM
A), arsine (As ₃ ) was used as the arsenic raw material, and monomethylhydrazine was used as the nitrogen raw material. Silane (SiH ₄ ) was used for n-type doping, and dimethyl zinc (DMZ) was used for p-type doping. When using phosphorus, phosphine (PH ₃ ) is used.

In the growth by MOCVD, only the portion of the active layer 14 is supplied by ALE in which a group III material and a group V material are alternately supplied.
Method (Atomic Layer Epitaxy) was adopted. Thereby, the thickness can be controlled at the atomic layer level, and a good superlattice can be formed.

Using this wafer, an oscillation wavelength of 1.2 μm
Of a Fabry-Perot LD having a stripe width of 3 μm. When the characteristic temperature (T ₀ ) of the threshold value of the laser was measured, a large increase of 120 K was confirmed. The threshold value is reduced by about 15% by reducing the In composition of the superlattice portion and introducing tensile strain.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
It is a figure which shows the band structure of the superlattice LD and the structure of a superlattice which concern on embodiment.

This embodiment is a modification of the first embodiment.
This is an example in which a strained quantum well structure is introduced into the active layer 14. The active layer 14 of this embodiment includes a well layer 14a and a barrier layer 14b.
Are alternately stacked, and the light guide layers 14c formed on both sides of the triple quantum well structure.

The well layer 14a is composed of a first superlattice in which a GaAs layer 141 of 2.5 nm and an InGaN layer 142 of 0.5 nm are alternately laminated, and the thickness of one well layer is 10 μm.
nm. The barrier layer 14b includes a 2.7-nm GaAs layer 141 and a 0.3-nm InGaAs layer 142.
Are alternately stacked, and one barrier layer has a thickness of 15 nm. Light guide layer 14c
Consists of a third superlattice having the same structure as the second superlattice,
It is formed to a thickness of 100 nm.

The oscillation wavelength in this embodiment is shorter than that of the first embodiment and is about 1.1 μm due to the quantum effect. When a Fabry-Perot LD having an oscillation wavelength of 1.1 μm and a stripe width of 3 μm was manufactured using this wafer, an increase in the threshold characteristic temperature (T ₀ ) was confirmed, as in the first embodiment. Was.

(Third Embodiment) FIG. 3 shows a third embodiment of the present invention.
FIG. 6 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to the embodiment.

This embodiment is a modification of the first embodiment.
The strain is applied to the well layer. That is, the well layer 14a
In addition, In is added to the GaAs portion of the first superlattice to introduce a compressive strain, and P is added to the GaAs portion of the second superlattice to introduce a tensile strain, thereby compensating the strain in the well layer 14a and the barrier layer 14b. ing. This makes it possible to form ten or more quantum wells. Oscillation wavelength is shorter and about 1.0
μm.

(Fourth Embodiment) FIG. 4 shows a fourth embodiment of the present invention.
FIG. 6 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to the embodiment. This is an example of forming a 1.5 μm laser.

As in the first embodiment, the GaAs substrate 1
1 is formed up to a GaAlAs cladding layer 13, and an InG layer having an emission wavelength of 1.2 μm lattice-matched to GaAs is formed thereon.
The super lattice of the aAsP layer 171 and the GaInN layer 172 is 10
The active layer 17 is grown to a thickness of 0 nm. I
The thickness of the nGaAsP layer 171 is 5.0 nm, and GaInN
Layer 172 has a thickness of 0.9 nm.

In this embodiment, the portion of the superlattice is InGa
The band gap is wider than AsP, and the oscillation wavelength is 1.
LDs of 3 to 1.6 μm were produced. (Fifth Embodiment) FIG. 5 is a diagram showing a semiconductor laminated structure of a superlattice LD according to a fifth embodiment of the present invention. This is an example of constructing a 680-720 nm laser.

An InGaP cladding layer 83 is formed on a GaAs substrate 11 with an n-type GaAs buffer layer 12 interposed therebetween, and a superlattice of an InGaP layer 181 and an InGaN layer 182 having lattice matching with GaAs or having a slightly larger lattice constant is formed thereon. And this is used as the active layer 18. In
The thickness of the GaP layer 181 is 5.0 nm,
The thickness of 2 is 0.9 nm.

(Sixth Embodiment) FIG. 6 shows a sixth embodiment of the present invention.
FIG. 6 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to the embodiment. This simplifies the structure of the first embodiment,
This is an example in which the oscillation wavelength is shortened.

An n-type GaAs cladding layer 93 is formed on a GaAs substrate 11 with an n-type GaAs buffer layer 12 interposed therebetween, and a superlattice of a GaAs layer 191 and a GaN layer 192 is grown thereon to form an active layer 19. ing. GaAs layer 19
1 has a thickness of 4.0 nm, and the GaN layer 192 has a thickness of 0.7
nm.

In the present embodiment, GaAs can be used as the cladding to increase the wavelength due to the effect of the incorporation of N, which facilitates its manufacture. Oscillation wavelength is 0.95 to 1.0 μm
Suitable for practical use.

(Seventh Embodiment) FIG. 7 shows a seventh embodiment of the present invention.
It is a figure showing the semiconductor lamination structure of the super lattice LED concerning an embodiment. This embodiment is an example in which the effect of increasing the band gap is used, contrary to the conventional example in which the band gap is reduced by mixing nitrogen.

If the amount of nitrogen is increased to some extent, the band gap becomes larger than that of the original arsenide or phosphide. By utilizing this effect, a cladding layer is formed by the first superlattice 21 and an active layer is formed by the second superlattice 22.

The first superlattice 21 is composed of a 3 nm InGaP layer 211 and a 1.5 nm GaN layer 212, and the second superlattice 22 is composed of a 4 nm InGaP layer 221 and a 1 nm GGaP layer.
An aN layer 222 is formed. The emission wavelength is 570 nm, which is shorter than the wavelength of InGaP, and can be used for green LEDs.

(Eighth Embodiment) FIG. 8 shows an eighth embodiment of the present invention.
FIG. 6 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to the embodiment. This is an example of using a superlattice in which As is mixed into a nitride, which is contrary to the conventional case.

When GaN is grown on the GaAs substrate 11 at a temperature of about 600 ° C. and at a low growth rate of 0.1 nm / hr, a diamond structure is formed. By combining this with GaAs, stable cubic GaN is realized.

The first superlattice 31 forming the cladding is
The GaN layer 311 of 3 nm and the GaAs 312 of 1 nm are used.
An aN layer 321 and a 1 nm GaAs layer 322 were used. Thereby, the wavelength of 530 nm which is shorter than that of the seventh embodiment is obtained.
Is obtained.

Each layer was grown using a molecular beam epitaxy (MBE) apparatus equipped with a plasma source of nitrogen. (Ninth Embodiment) FIG. 9 is a view showing a semiconductor laminated structure of a superlattice LD according to a ninth embodiment of the present invention. This is an example in which an element oscillating at 1.5 to 3 μm in the infrared region is formed on an InP substrate.

An InP cladding layer 42 is formed on an InP substrate 41.
Is grown, and a 2.5 nm InGaAs layer 441 and 0.5
A 100 nm superlattice active layer 44 composed of a 100 nm InGaN layer 442 was grown.

In this embodiment, since the InGaAs layer 441 is lattice-matched with InP, the oscillation wavelength is longer than that of the conventional InGaAsP-based semiconductor. (Tenth Embodiment) FIG. 10 is a diagram showing a semiconductor laminated structure of a superlattice LD according to a tenth embodiment of the present invention. This is an example using a GaP substrate.

A GaP cladding layer 52 is formed on a GaP substrate 51.
Is grown to form a short-period superlattice 54 composed of a 1.5-nm GaP layer 541 and a 0.7-nm GaN layer 542 for 250 n.
m.

In this embodiment, an LED that emits light at 580 nm longer than the wavelength of GaP is produced by mixing N. Due to the incorporation of N, the GaPN band approaches the direct transition type, and the luminous efficiency is higher than that of the conventional N-doped GaP LED. There is an advantage that the cladding layer 52 can be made of GaP.

(Eleventh Embodiment) FIG. 11 is a view showing a semiconductor laminated structure of a superlattice LD according to an eleventh embodiment of the present invention. This is an example using a silicon substrate.

Since GaPN lattice-matches with silicon, heteroepitaxy on silicon can be performed relatively easily.
GaP buffer layer 6 grown at low temperature on silicon substrate 61
And a first superlattice 64 comprising a 1.5 nm GaP layer 641 and a 0.5 nm GaN layer 642 thereon.
Is formed as a cladding layer, and a 1.5 nm GaP layer 67 is formed.
A second superlattice 67 composed of a 1 and 0.7 nm GaN layer 672 was formed to form an active layer.

(Twelfth Embodiment) FIG. 12 is a view showing a semiconductor laminated structure of a superlattice LD according to a twelfth embodiment of the present invention. This is an example in which the eleventh embodiment is improved.

The second superlattice forming the active layer is made of GaAs.
The layer 741 and the GaN layer 742 form a superlattice 74. The GaP buffer layer 62 also serves as the cladding layer. In the case of the present embodiment, the emission wavelength is as long as 0.9 to 1.1 μm,
Since the band of the active layer 74 is completely of a direct transition type, the efficiency is higher by one digit or more, and the band gap difference with the cladding layer 62 can be made large, so that an LD with high temperature characteristics can be manufactured on a silicon substrate.

The present invention is not limited to the above embodiments. It is applicable to all combinations of nitrides and mixtures that are difficult to mix, such as phosphorus and arsenide. In the embodiment, the case where the present invention is applied to an LD or an LED has been described. However, the present invention is not limited to an optical semiconductor element and can be applied to various electronic devices. In addition, without departing from the gist of the present invention,
Various modifications can be made.

[0052]

As described above, according to the present invention, the first compound layer composed of the group V element and the group III element containing nitrogen and the second compound layer composed of the group V element and the group III element containing no nitrogen are included. Are alternately stacked to form a superlattice structure, whereby a compound thin film equivalent to a nitride, phosphorus and arsenide compound semiconductor, which could not be produced conventionally, can be grown. Therefore, application to new light emitting elements and electronic devices can be expected, and its usefulness is great.

[Brief description of the drawings]

FIG. 1 is a view showing a semiconductor laminated structure of a superlattice LD according to a first embodiment.

FIG. 2 is a diagram showing a band structure of a superlattice LD and a structure of a superlattice according to a second embodiment.

FIG. 3 is a diagram showing a semiconductor laminated structure of a superlattice LD according to a third embodiment.

FIG. 4 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to a fourth embodiment.

FIG. 5 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to a fifth embodiment.

FIG. 6 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to a sixth embodiment.

FIG. 7 is a view showing a semiconductor laminated structure of a super lattice LED according to a seventh embodiment.

FIG. 8 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to an eighth embodiment.

FIG. 9 is a view showing a semiconductor multilayer structure of a superlattice LD according to a ninth embodiment.

FIG. 10 is a diagram showing a semiconductor laminated structure of a superlattice LD according to a tenth embodiment.

FIG. 11 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to an eleventh embodiment.

FIG. 12 is a diagram showing a semiconductor multilayer structure of a superlattice LD according to a twelfth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... n-type GaAs substrate 12 ... n-type GaAs buffer layer 13 ... n-type GaAlAs clad layer 14 ... active layer 15 ... p-type GaAlAs clad layer 16 ... p-type GaAs contact layer 17 ... Active layer consisting of a superlattice of InGaAsP and InGaN Reference Signs List 18 active layer composed of InGaP and InGaN superlattices 19 active layer composed of GaAs and GaN superlattices 21 cladding layer composed of InGaP and GaN 22 active layer composed of InGaP and GaN 31 cladding composed of GaN and GaAs Layer 32: Active layer composed of GaN and GaAs 41: InP substrate 42: InP clad layer 44: Active layer composed of a superlattice of InGaAs and InGaN 51: GaP substrate 52: GaP clad layer 54: composed of a superlattice of GaP and GaN Active layer 61 ... Si substrate 62 ... G P buffer layer 64: cladding layer composed of GaP and GaN superlattices 67: active layer composed of GaP and GaN superlattices 74: active layer composed of GaAs and GaN superlattices 83: InGaP cladding layer 93: GaAs cladding layer 141 , 191, 741... A part of the GaAs layer (second compound layer) of the superlattice 142, 182, 442... A part of the InGaN layer (first compound layer) 181, 211, 221. Part of InGaP layer (second compound layer) 192, 212, 222...
441: a part of the superlattice InGaAs layer (second compound layer) 541, 641, 671 ... a part of the superlattice GaP layer (second compound layer) 542, 642, 672, 742 ... Some Ga in the superlattice
N layer (first compound layer)

Claims (5)

[Claims] 1. A compound semiconductor device in which a plurality of semiconductor thin films made of a group III-V compound semiconductor are stacked on a single crystal substrate, wherein at least a part of the plurality of semiconductor thin films includes a group V element containing nitrogen and a group III element. A first compound layer made of a group III element and a second compound layer made of a group V element and a group III element that do not contain nitrogen are alternately laminated; A compound semiconductor device wherein a portion farther from the substrate and the lattice constant is formed thinner than a portion closer to the substrate and the lattice constant. 2. The compound semiconductor device according to claim 1, wherein a thinner one of the first and second compound layers has a thickness of 5 nm or less. 3. The compound semiconductor device according to claim 1, wherein said substrate is made of GaAs or InP, and said first compound layer is formed thinner than said second compound layer. 4. The compound semiconductor device according to claim 1, wherein said substrate is made of GaP or Si, and said second compound layer is formed thinner than said first compound layer. 5. The first compound layer is formed of Al _{v G aw} In _1-vw.
N (0 ≦ v, w ≦ 1), and the second compound layer is Al _{x
Ga y In 1-xy As z} P 1-z (0 ≦ x, y, z ≦ 1)
The compound semiconductor device according to claim 1, wherein