JPH07302764A - Growing method of ii-vi group compound semiconductor - Google Patents

Abstract

PURPOSE:To grow p or n type II-VI group compound semiconductor in sufficiently high acceptor or donor concentration. CONSTITUTION:A p type ZnSe layer can be grown by alternately repeating the following two steps i.e., the first step of simultaneously feeding Zn material as II group element, Se material as VI group material and N dopant as an acceptor impurities to a reaction tube of an MOCVD device alltogether to form ZnSe:N layer 24 and the second step of forming the Zn and N adsorbed layer 23 when the feeding of Se material is stopped while the feeding of Zn material and N dopant is being kept on.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a II-VI group compound semiconductor, and is suitable for use in manufacturing a light emitting device such as a semiconductor laser or a light emitting diode using a II-VI group compound semiconductor. It is a thing.

[0002]

2. Description of the Related Art In recent years, in order to improve the recording density of optical discs and the resolution of laser printers, there is an increasing demand for semiconductor lasers capable of emitting light at short wavelengths, and research aimed at realizing them has been made. It is active.

A II-VI group compound semiconductor is promising as a material used for producing a semiconductor laser capable of emitting light at such a short wavelength. In particular, the ZnMgSSe-based compound semiconductor, which is a quaternary II-VI group compound semiconductor, is
It is known to be suitable as a material for a clad layer and an optical waveguide layer when a blue or green emitting semiconductor laser having a wavelength of 400 to 550 nm is formed on a GaAs substrate (for example, Electron. Lett. 28 (1992). ) 1798).

Until now, the growth of II-VI group compound semiconductors has been carried out exclusively by the molecular beam epitaxy (MBE) method, but this MBE method is unsatisfactory in terms of productivity. Therefore, in recent years, an attempt has been made to apply a metal organic chemical vapor deposition (MOCVD) method, which has excellent productivity and is widely used as a method for growing a III-V group compound semiconductor, to the growth of a II-VI group compound semiconductor. .

Conventionally, the growth of II-VI group compound semiconductors by MOCVD has been carried out as follows. For example, when p-type ZnSe is grown, an organometallic compound such as dimethylzinc (DMZn) or diethylzinc (DEZn) is used as a raw material of Zn which is a group II element, and dimethylselenium is used as a raw material of Se which is a group VI element. (DMS
e) or an organometallic compound such as diethyl selenium (DESe) or a hydrogen compound such as hydrogen selenide (H ₂ Se), ammonia (NH ₃ ) or hydrazine (N) as a p-type dopant containing nitrogen (N) serving as an acceptor impurity. ₂
H _4), tertiary butyl amine (t-BNH _2), compounds such as diisopropylamine (Di-PNH) is used. Then, these Zn raw material, Se raw material, and p-type dopant are simultaneously supplied in a gas state into the reaction tube, placed on a susceptor installed in the reaction tube in advance, and p-type ZnSe is heated on a substrate heated to a predetermined temperature. Growth takes place.

[0006]

In the above-mentioned growth of p-type ZnSe, Zn of N contained in the p-type dopant is used.
Incorporation into Se is very important. However,
In the above-mentioned conventional MOCVD growth, Zn
The incorporation efficiency of N into Se is very low, which is due to secondary ion mass spectrometry (SIMS) and photoluminescence (P
L) and the like. Due to such a problem, it was difficult to obtain p-type ZnSe having a sufficiently high concentration of N as an acceptor impurity.

Further, when the II-VI group compound semiconductor containing Mg such as ZnMgSSe is grown by the MOCVD method, the growth temperature must be relatively high, but the incorporation efficiency of N into the grown crystal is high. It tends to get worse. Therefore, II containing this Mg
It is more difficult to obtain a —VI compound semiconductor having a sufficiently high concentration of N as an acceptor impurity.

As described above, I by the conventional MOCVD method is used.
Depending on the method of growing the group I-VI compound semiconductor, it was difficult to obtain a p-type group II-VI compound semiconductor having a sufficiently high acceptor concentration. Furthermore, a similar problem is n
It also exists when growing a type II-VI compound semiconductor. For example, it has been difficult to grow ZnTe having a sufficiently high donor concentration by the conventional MOCVD method.

As described above, it is difficult to grow a p-type or n-type II-VI group compound semiconductor having a sufficiently high acceptor concentration or donor concentration.
Since there is a great obstacle in manufacturing a light emitting device such as a semiconductor laser or a light emitting diode using a Group I compound semiconductor, improvement thereof has been desired.

Therefore, an object of the present invention is to grow a p-type or n-type II-VI group compound semiconductor having a sufficiently high acceptor concentration or donor concentration.
A method of growing a group I-VI compound semiconductor is provided.

[0011]

In order to achieve the above object, the present invention provides a II-VI by a vapor phase growth method using a group II element raw material, a group VI element raw material and a dopant.
A method for growing a II-VI compound semiconductor for growing a group compound semiconductor, comprising the step of interrupting the growth by interrupting the supply of one of the group II element raw material and the group VI element raw material. It is what

In one embodiment of the present invention, the supply of the Group II element raw material and the supply of the dopant are maintained, and V
The growth is interrupted by interrupting the supply of the raw material of the group I element. In this case, the acceptor impurity or the donor impurity contained in the dopant enters the site of the VI group element of the II-VI compound semiconductor to be grown. For example, when using a p-type dopant containing nitrogen (N) as an acceptor impurity, this N enters the site of the VI group element of the II-VI group compound semiconductor to be grown.

In another embodiment of the present invention, V
The supply of the raw material of the group I element and the supply of the dopant are maintained, and the growth is interrupted by interrupting the supply of the raw material of the group II element. In this case, acceptor impurities or donor impurities contained in the dopant enter the site of the group II element of the grown group II-VI compound semiconductor. For example, when a p-type dopant containing lithium (Li) or sodium (Na) serving as an acceptor impurity is used, this Li
Alternatively, Na enters the group II element site of the grown II-VI compound semiconductor.

In the present invention, after supplying only the raw material of the group II element, the supply of the raw material of the group II element is interrupted,
You may make it supply only a dopant. In this case, the acceptor impurity or the donor impurity contained in the dopant is V of the II-VI group compound semiconductor to be grown.
Enter the group I element site.

Further, in the present invention, after supplying only the raw material of the group VI element, the supply of the raw material of the group VI element may be interrupted to supply only the dopant.
In this case, the acceptor impurity or the donor impurity contained in the dopant enters the site of the II group element of the II-VI group compound semiconductor to be grown.

Further, in the present invention, the reaction by-products of the group VI element raw material and the dopant may be prevented from being produced by not simultaneously supplying the group VI element raw material and the dopant.

Alternatively, in the present invention, the reaction by-product of the group II element raw material and the dopant may not be generated by not supplying the group II element raw material and the dopant at the same time.

In the present invention, the vapor phase growth method is as follows:
In addition to the metal organic chemical vapor deposition method, a molecular beam epitaxy method using a gas source can be used.

Further, in the present invention, the grown II
Group VI compound semiconductors include, for example, Zn _1-ab Mg _a Cd
_b S _c Te _d Se _1-cd compound semiconductor (where 0 ≦
a, b, c, d <1), and more specifically ZnS
e, ZnSSe, ZnCdSe, ZnMgSSe and the like.

In the method of growing a compound semiconductor by the MOCVD method or the MBE method, the growth can be interrupted regularly and stably. These MOCVD method and MBE method are suitable for interrupting the growth because the source material to be supplied can be easily controlled and the surface of the epitaxial layer is not contaminated during the interrupting of the growth. There is.

Further, when the growth is interrupted in the growth by the MOCVD method, there remains a problem that the raw material gas remains in the reaction tube during the growth interruption. This problem can be solved by increasing the flow rate of the raw material gas. You can That is,
If the flow rate of the raw material gas is set to, for example, about 50 cm / sec, and the growth rate of the epitaxial layer at this time is 0.1 nm / sec, the raw material gas is set to about 5 cm for a substrate. Since the gas passes through in about 0.1 seconds, the source gas hardly remains during the growth interruption, and the growth hardly occurs even under the condition of the growth rate of about 0.1 nm / second.

[0022]

II-according to the present invention constructed as described above
According to the method for growing a Group VI compound semiconductor, the method includes the step of interrupting the growth by interrupting the supply of one of the Group II element raw material and the Group VI element raw material. In the case where the element raw material or dopant is a p-type dopant containing an acceptor impurity that enters the site of the Group VI element of the II-VI group compound semiconductor, a bond between the Group II element and the acceptor impurity is forcibly formed, and , The raw material for interrupting the supply is the raw material of the II group element, and the dopant is II of the II-VI compound semiconductor.
In the case of a p-type dopant containing an acceptor impurity that enters a group element site, a bond between the group VI element and the acceptor impurity is forcibly formed. Therefore, it is possible to increase the efficiency of incorporating the acceptor impurities into the grown II-VI compound semiconductor. Also grown I
The incorporation efficiency of the donor impurity into the I-VI group compound semiconductor can be similarly increased. Further, according to this growth method, it is possible to increase the acceptor impurity or donor impurity uptake efficiency even at a high growth temperature, and for example, II-V containing Mg such as ZnMgSSe.
It is possible to increase the efficiency of incorporating N into the group I compound semiconductor.

As described above, it is possible to grow a p-type or n-type II-VI group compound semiconductor having a sufficiently high acceptor concentration or donor concentration. Further, particularly when the MOCVD method is used as the vapor phase growth method, the II-VI group compound semiconductor can be grown with high productivity.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. First, the MOCVD apparatus used in the first embodiment of the present invention will be described. FIG. 1 shows the structure of the MOCVD apparatus.

As shown in FIG. 1, in this MOCVD apparatus, hydrogen (H ₂ ) gas highly purified by the H ₂ purifying apparatus 1 is supplied into the bubblers 2, 3 and 4 as a carrier gas. Now, considering the case of growing p-type ZnSe, in these bubblers 2, 3 and 4, for example, DMZn as a Zn raw material, DMSe as a Se raw material, and Di-PNH as a p-type dopant are respectively provided.
Is included. H ₂ in these bubblers 2, 3, 4
By supplying gas, these bubblers 2, 3,
A raw material gas corresponding to the vapor pressure is supplied from each of 4 together with H ₂ gas as a carrier gas into the reaction tube 6 through the reaction tube line 5. A susceptor 7 is provided in the reaction tube 6.
Is placed and the substrate 8 is placed thereon.

Reference numeral 9 indicates a vent line. in this case,
Switching between the reaction tube line 5 of the source gas generated from the bubbler 2 and the vent line 9 can be performed by opening / closing the valves V ₁ and V ₂ , and the reaction tube line of the source gas generated from the bubbler 3 5 and the vent line 9 can be switched by opening and closing the valves V ₃ and V ₄ , and the dopant gas generated from the bubbler 4 can be switched between the reaction tube line 5 and the vent line 9. Valve V
₅ , V ₆ can be opened and closed. Note that reference numerals 10 to 14 denote mass flow controllers for controlling the flow rate of the H ₂ gas supplied from the H ₂ purifying device 1.

FIG. 2 shows a p-type Z according to the first embodiment of the present invention.
It is a sequence diagram which shows the state of supply of the source gas and the dopant gas in the growth method of nSe. Also, FIG.
A to E are t = t ₁ , t ₂ , t ₃ , t _{4 in FIG} .
The state of the growth layer at each time t ₅ is shown.

Hereinafter, with reference to FIGS. 1, 2 and 3,
A method for growing p-type ZnSe according to the first embodiment will be described.

First, a GaAs substrate 21 is placed as a substrate 8 on the susceptor 7 in the reaction tube 6 of the MOCVD apparatus shown in FIG. 1, and the GaAs substrate 21 is heated by the susceptor 7 to the growth temperature in the H ₂ gas atmosphere.

Next, DM as a Zn raw material is placed in the reaction tube 6.
As shown in FIG. 3A, by supplying ZnSe, DMSe as a raw material, and Di-PNH as a p-type dopant, an N-doped ZnSe layer (hereinafter referred to as “ZnSe: N layer”) is formed on the GaAs substrate 21. 22)
Are grown epitaxially. This ZnSe: N layer 22
Epitaxial growth is from time t = 0 to time t = t ₁
Up to (Fig. 2). This first epitaxially grown ZnSe: N layer 22 is a ZnS: N layer 22 that is subsequently grown.
e: It becomes a buffer layer of N layers.

Next, at time t = t ₁ , the supply of DMSe is interrupted while maintaining the supply of DMZn and Di-PNH to suspend the growth. This growth interruption occurs at time t =
Perform until t ₂ . During this growth interruption, ZnZn is adsorbed on the surface of the ZnSe: N layer 22 as a buffer layer due to thermal decomposition of DMZn supplied into the reaction tube 6, and the surface is covered with the Zn adsorbed layer. Zn in Zn adsorption layer
N adsorbed by the thermal decomposition of Di-PNH is adsorbed on, and N is taken into the growth layer. In this case, since the bond between Zn and N is forcibly formed,
The N uptake efficiency is high. In FIG. 3B, the adsorption layer of Zn and N is indicated by reference numeral 23.

Next, at time t = t ₂ , the supply of DMSe into the reaction tube 6 is restarted, and this D is maintained until time t = t _3.
Continue to supply MSe. As a result, all of DMZn, DMSe and Di-PNH are simultaneously supplied into the reaction tube 6, and the ZnSe: N layer 24 is thinly epitaxially grown as shown in FIG. 3C.

Next, at time t = t ₃ , DM
DMSe while maintaining the supply of Zn and Di-PNH
Supply is suspended and growth is suspended. During this growth interruption, as shown in FIG. 3D, an adsorption layer 23 of Zn and N is formed on the surface of the ZnSe: N layer 24.

Next, at time t = t ₄ , the supply of DMSe into the reaction tube 6 is restarted, and this D is supplied until time t = t _5.
Continue to supply MSe. As a result, all of DMZn, DMSe and Di-PNH are simultaneously supplied into the reaction tube 6, and again the ZnSe: N layer 2 is formed as shown in FIG. 3E.
4 is thinly epitaxially grown.

As described above, the growth interruption is performed to form the adsorption layer 23 of Zn and N, and the step of epitaxially growing the ZnSe: N layer 24 thinly thereon is repeated a necessary number of times to obtain a desired thickness as a whole. With ZnS
The e: N layer 24 is epitaxially grown.

FIG. 4 shows a photoluminescence spectrum of the ZnSe: N layer 24 epitaxially grown as described above. However, the measurement temperature is 4.2K (liquid helium temperature). The supply amount of DMZn, DMSe and Di-PNH is 9.5 μmol / each.
Min, 38.4 μmol / min and 70.5 μmol / min.

On the other hand, for comparison, as in the case of the conventional MOCVD epitaxial growth method, as shown in the sequence diagram of FIG. 5, DMZn, DMSe and Di-
As shown in FIG. 6, a sample was prepared by epitaxially growing a ZnSe: N layer 24 having a required thickness while simultaneously supplying all of PNH, and the ZnSe: N layer 2 was formed.
The photoluminescence spectrum of 4 was measured. The result is shown in FIG. 7. However, the measurement temperature is 4.2K (liquid helium temperature). The supply amount of DMZn, DMSe and Di-PNH is 9.5 μmol / each.
Min, 38.4 μmol / min and 141 μmol / min. It should be noted that the vertical scale full scales in FIGS. 4 and 7 are different from each other.

The greatest difference between FIG. 4 and FIG. 7 is that
The intensities of DAP (donor-acceptor pair) emission observed near a wavelength of 460 nm are greatly different from each other, which is much higher in FIG. 4 than in FIG. 7. This DAP emission is evidence that it is N-doped,
The greater the strength, the greater the N doping amount. From FIG. 4 and FIG. 7, the N raw material (Di
ZnS grown by the growth method according to the first embodiment even though the supply amount of —PNH) is half.
The intensity of the DAP emission of the e: N layer 24 is DMZn, DMS.
ZnSe grown by a conventional growth method of growing while simultaneously supplying all of e and Di-PNH:
It can be seen that it is about several times larger than that of the N layer 24, and thus is doped with a larger amount of N. Specifically, ZnSe: N grown by the conventional growth method is used.
N _A −N _D of the layer 24 = 2 × 10 ¹⁶ cm ⁻³ (however,
N _A : acceptor concentration, N _D : donor concentration)
Z grown by the growth method according to the first embodiment
N _A -N _D of the nSe: N layer 24 is several times higher than that.

In FIGS. 4 and 7, peaks other than the DAP emission are I ₁ (neutral acceptor bound excitons).
Light emission, phonon replica of DAP light emission, and Y light emission (light emission due to misfit dislocations).

As described above, according to the growth method of the first embodiment, ZnSe: N is supplied while simultaneously supplying all of ZnZn source DMZn, Se source DMSe, and N dopant Di-PNH. The step of growing the layer 24 and the step of forming the N and Zn adsorption layer 23 by interrupting the growth by interrupting the DMSe supply while maintaining the supply of DMZn and Di-PNH are alternately performed. Since it is repeated, N to ZnSe
The efficiency of uptake of N
ZnSe: N layer 2 of a required thickness heavily doped with
4, that is, a p-type ZnSe layer can be grown.

Next, a second embodiment in which the present invention is applied to manufacture of a semiconductor laser using a II-VI group compound semiconductor will be described. The semiconductor laser manufactured by the second embodiment is a so-called SCH (Separate Confineme).
nt Heterostructure) structure.

8 and 9 show a semiconductor laser manufactured according to the second embodiment. Here, FIG. 8 is a sectional view perpendicular to the cavity length direction of this semiconductor laser, and FIG. 9 is a sectional view parallel to the cavity length direction of this semiconductor laser.

As shown in FIGS. 8 and 9, in the method of manufacturing a semiconductor laser according to the second embodiment, first, for example, n-type GaAs having a (100) plane orientation doped with silicon (Si) as a donor impurity. The n-type ZnSe buffer layer 3 doped with iodine (I), for example, as a donor impurity by the MOCVD method including the step of interrupting the growth similar to that of the first embodiment described above on the substrate 31.
2, for example, n-type Z doped with I as a donor impurity
From the n _1-p Mg _p S _q Se _1-q cladding layer 33, for example, an n-type ZnSe optical waveguide layer 34 doped with I as a donor impurity, such as an intrinsic (i-type) Zn _1-z Cd _z Se quantum well layer. Active layer 35, for example, p-type ZnSe optical waveguide layer 36 doped with N as an acceptor impurity, for example, p-type Zn _1-p M doped with N as an acceptor impurity
g _p S _q Se _1-q clad layer 37, for example, p-type ZnS _v Se _1-v layer 3 doped with N as an acceptor impurity
8, for example, p doped with N as an acceptor impurity
-Type ZnSe contact layer 39, for example, p-type ZnTe / ZnSe multiple quantum well (MQW) in which quantum well layers made of p-type ZnTe doped with N as an acceptor impurity and barrier layers made of p-type ZnSe are alternately stacked.
The layer 40 and a p-type ZnTe contact layer 41 doped with N as an acceptor impurity, for example, are sequentially epitaxially grown. p-type ZnTe / ZnSe MQW layer 40
Will be described in detail later.

In this case, in the epitaxial growth of the n-type ZnSe buffer layer 32 and the n-type ZnSe optical waveguide layer 34, for example, DMZn is used as a Zn raw material, DMSe is used as the Se raw material, and ethyl iodide is used as a dopant for I. In the epitaxial growth of the n-type Zn _1-p Mg _{p Sq} Se _1-q cladding layer 33, for example, Zn
DMZn as a raw material, bismethylcyclopentadienyl magnesium ((MeCp) ₂ Mg) as a Mg raw material,
Diethyl sulfur (DES) is used as the S raw material, DMSe is used as the Se raw material, and ethyl iodide is used as the dopant for I. Further, in the epitaxial growth of the active layer 35 composed of the i-type Zn _1-z Cd _z Se quantum well layer, for example, DMZn as a Zn raw material, dimethylcadmium (DMCd) as a Cd raw material, and DMSe as an Se raw material are used.
To use.

P-type ZnSe optical waveguide layer 36, p-type ZnSe
Contact layer 39 and p-type ZnTe / ZnSe MQW
In the epitaxial growth of the p-type ZnSe layer of the layer 40, for example, DMZn is used as the Zn raw material, DMSe is used as the Se raw material, and Di-PNH is used as the N dopant. p-type Zn _1-p Mg _p S _q Se _1-q clad layer 37
In the epitaxial growth of, for example, DMZn as a Zn raw material, (MeCp) ₂ Mg, S as a Mg raw material,
DES is used as a raw material, DMSe is used as a Se raw material, and Di-PNH is used as a dopant for N. Also, p-type Z
In the epitaxial growth of the nS _v Se _1-v layer 38, for example, ZnZn raw material is DMZn and S raw material is H
₂ DMSe as the S and Se raw materials and Di-PNH as the N dopant. Furthermore, p-type ZnTe / Z
p-type ZnTe layer and p-type ZnT of nSeMQW layer 40
In the epitaxial growth of the e-contact layer 41,
For example, DMZn as a Zn raw material, diethyl tellurium (DETe) as a Te raw material, and D as a N dopant.
i-PNH is used.

In the epitaxial growth of the n-type ZnSe buffer layer 32 and the n-type ZnSe optical waveguide layer 34, a step of growing while simultaneously supplying DMZn, DMSe and ethyl iodide, for example, supplying DMZn and ethyl iodide. The process of suspending the growth by suspending the supply of DMSe while maintaining the above condition is repeated. In the epitaxial growth of the n-type Zn _1-p Mg _p S _q Se _1-q cladding layer 33, DMZn, (MeC
p) a step of growing while simultaneously supplying ₂ Mg, DES, DMSe and ethyl iodide;
The step of interrupting the growth by interrupting the supply of DES and DMSe while maintaining the supply of (MeCp) ₂ Mg and ethyl iodide is repeated.

Further, the p-type ZnSe optical waveguide layer 36, the p-type ZnSe contact layer 39, and the p-type ZnTe / ZnS.
In the epitaxial growth of the p-type ZnSe layer of the eMQW layer 40, by performing the growth while simultaneously supplying DMZn, DMSe and Di-PNH, and by interrupting the supply of DMSe while maintaining the supply of DMZn and Di-PNH. The step of interrupting the growth is repeated. Furthermore, in the epitaxial growth of the p-type Zn _1-p Mg _p S _q Se _1-q cladding layer 37, DMZ is used.
n, (MeCp) ₂ Mg, DES, DMSe and Di
-Growing while simultaneously supplying PNH and DM
The step of interrupting the growth by interrupting the supply of DES and DMSe while maintaining the supply of Zn, (MeCp) ₂ Mg and Di-PNH is repeated. Also,
In the epitaxial growth of the p-type ZnS _v Se _1-v layer 38, DMZn, DES, DMSe and Di-PN are used.
A step of growing while supplying H simultaneously, and DES and D while maintaining the supply of DMZn and Di-PNH.
The step of interrupting the growth by interrupting the supply of MSe is repeated. Furthermore, p-type ZnTe / ZnSeM
In the epitaxial growth of the p-type ZnTe layer of the QW layer 40 and the p-type ZnTe contact layer 41, DMZ is used.
The step of growing while simultaneously supplying n, DETe and Di-PNH and the step of interrupting growth by interrupting the supply of DETe while maintaining the supply of DMZn and Di-PNH are repeated.

Next, a stripe-shaped resist pattern (not shown) having a predetermined width is formed on the p-type ZnTe contact layer 41, and the p-type ZnS _v Se _1-v layer 38 is formed using this resist pattern as a mask. Etching is performed up to a middle depth in the thickness direction by, for example, a wet etching method. As a result, the upper layer of the p-type ZnS _v Se _1-v layer 38, the p-type ZnSe contact layer 39, and the p-type ZnTe / Z
nSe MQW layer 40 and p-type ZnTe contact layer 4
1 is patterned into a stripe shape. The width of this stripe portion is, for example, 5 μm.

Next, an alumina (Al ₂ O ₃ ) film having a thickness of 300 nm, for example, was vacuum-deposited on the entire surface while leaving the resist pattern used for the above etching, and then the resist pattern was formed thereon. It is removed together with the Al ₂ O ₃ film (lift-off). As a result, the insulating layer 42 made of the Al ₂ O ₃ film is formed only on the p-type ZnS _v Se _1-v layer 38 other than the stripe portion.

Next, the stripe-shaped p-type ZnTe contact layer 41 and the insulating layer 42 have a thickness of, for example, 1 on the entire surface.
A 0 nm Pd film, for example, a Pt film having a thickness of 100 nm and an Au film having a thickness of 300 nm, for example, are sequentially vacuum-deposited to form a p-side electrode 43 composed of a Pd / Pt / Au electrode.
Then, if necessary, heat treatment is performed to remove the p-side electrode 43.
Is ohmic-contacted with the p-type ZnTe contact layer 41. A portion of the p-side electrode 43 in contact with the p-type ZnTe contact layer 41 serves as a current path. On the other hand, an n-side electrode 44 such as an In electrode is formed on the back surface of the n-type GaAs substrate 31.

Next, the n-type GaAs substrate 31 having the laser structure formed as described above is cleaved in a bar shape to form both resonator end faces, and then the front surface from which laser light is extracted, for example, by a vacuum deposition method. Al ₂ to the cavity end face side
A multi-layered film composed of an O ₃ film 45 and a Si film 46 is formed, and a multi-layered film in which the Al ₂ O ₃ film 45 and the Si film 46 are repeated for two cycles is formed on the end face of the resonator on the rear side from which laser light is not extracted. Form. Here, the Al ₂ O ₃ film 45 and Si
The thickness of the multilayer film including the film 46 is selected so that the optical distance obtained by multiplying the refractive index by the film is ¼ of the oscillation wavelength of the laser light. By applying such an end face coating, for example, the reflectance of the front end face is 70%,
The reflectance of the rear end face can be set to 95%. After the end face coating is applied in this manner, the bar is cleaved to form chips, and packaging is performed.

In the semiconductor laser according to the second embodiment, the thickness of the i-type Zn _1-z Cd _z Se quantum well layer constituting the active layer 35 is preferably 2 to 20 nm, for example 9n.
m.

Further, in this case, n-type Zn _1-p Mg _p S _q
Se _1-q cladding layer 33 and p-type Zn _1-p Mg _p S _q
The Mg composition ratio p of the Se _1-q clad layer 37 is, for example, 0.0
9, the S composition ratio q is, for example, 0.18, and the energy gap E _{g at} that time is about 2.94 eV at 77K. These n-type Zn _1-p Mg _p S _q Se _1-q having a Mg composition ratio p = 0.09 and an S composition ratio q = 0.18
Cladding layer 33 and p-type Zn _1-p Mg _p S _q Se _1-q
The cladding layer 37 is lattice-matched with GaAs. The Cd composition ratio z of the i-type Zn _1-z Cd _z Se quantum well layer forming the active layer 35 is, for example, 0.19, and the energy gap E _{g at} that time is about 2.54 eV at 77K.
At this time, the n-type Zn _1-p Mg _p S _q Se _1-q clad layer 33, the p-type Zn _1-p Mg _p S _q Se _1-q clad layer 37, and the i-type Zn _1- constituting the active layer 35 are formed. _z Cd _z Se quantum well layer energy gap E _g difference ΔE
_g is 0.40 eV. The value of the energy gap E _g at room temperature is the energy gap E at 77K.
It can be determined by subtracting 0.1 eV from the value of _g .

The thickness of the n-type Zn _1-p Mg _p S _q Se _1-q cladding layer 33 is, for example, 0.8 μm, and the n-type ZnSe is
The thickness of the optical waveguide layer 34 is, for example, 60 nm, the thickness of the p-type ZnSe optical waveguide layer 36 is, for example, 60 nm, and the p-type Zn _1-p Mg
The thickness of the _p S _q Se _1-q clad layer 37 is, for example, 0.6 μm.
The thickness of the m, p-type ZnS _v Se _1-v layer 38 is, for example, 0.6.
The thickness of the p-type ZnSe contact layer 39 is, for example, 4 μm.
The thickness of the p-type ZnTe contact layer 11 is 5 nm, and is 70 nm, for example.

Further, since the thickness of the n-type ZnSe buffer layer 32 has a slight lattice mismatch between ZnSe and GaAs, the n-type ZnSe buffer layer is caused by this lattice mismatch. In order to prevent dislocation from occurring during the epitaxial growth of the layer 32 and each of the layers thereon, it is selected to be sufficiently smaller than the critical film thickness of ZnSe (up to 100 nm), but here, for example, 33 nm is selected.

The p-type ZnS _v Se _1-v layer 38 on the p _- type Zn _1-p Mg _p S _q Se _1-q cladding layer 37 may be a p-type Zn _1-p Mg _p S layer depending on the case. functions as a second p-type cladding layer added to the _q Se _1-q cladding layer 37, a function of lattice matching with the p-type _{Zn 1-p Mg p S q} Se 1-q cladding layer 37, onto the heat sink It has one or two or more of the functions as a spacer layer for preventing a short circuit due to creeping up of solder on the chip end surface when mounting the laser chip. p-type Zn _1-p
Although there is a balance with the Mg composition ratio p and the S composition ratio q of the Mg _p S _q Se _1-q cladding layer 37, this p-type ZnS _v
The S composition ratio v of the Se _1-v layer 38 is selected within the range of 0 <v ≦ 0.1, preferably 0.06 ≦ v ≦ 0.08, and in particular, p-type Zn _1-p Mg _p S _The optimum S composition ratio v for achieving lattice matching with the _q Se _{1 -q} cladding layer 37 is 0.06.

The p-type ZnTe / ZnSe MQW layer 4 described above
The reason for providing 0 is that when the p-type ZnSe contact layer 39 and the p-type ZnTe contact layer 41 are directly bonded, a large discontinuity occurs in the valence band at the bonding interface, which is caused by the p-side electrode 43 to the p-type ZnTe contact layer 41. This is to effectively eliminate this barrier because it becomes a barrier to holes injected into the.

That is, the upper limit of the carrier concentration in p-type ZnSe is usually 5 × 10 ¹⁷ cm ^-3 , while p
The carrier concentration in the type ZnTe can be 10 ¹⁸ cm ⁻³ or more. In addition, p-type ZnSe / p-type ZnTe
The valence band discontinuity at the interface is about 0.5 eV
Is. The valence band of such a p-type ZnSe / p-type ZnTe junction, the junction is assumed to be a step junction, W = the p-type ZnSe side ^{_{(2εφ T / qN A) 1/2}} (1) Width The band is bent over. Here, ε is the dielectric constant of ZnSe, and φ _T is p-type ZnSe / p-type ZnTe.
Size of discontinuity in valence band at interface (about 0.5e
V) is represented.

When W is calculated in this case using the equation (1), W = 32 nm. FIG. 10 shows how the top of the valence band at this time changes along the direction perpendicular to the p-type ZnSe / p-type ZnTe interface. However, it is approximated that the Fermi levels of p-type ZnSe and p-type ZnTe coincide with the top of the valence band. As shown in FIG. 10, in this case, the valence band of p-type ZnSe is p-type Z.
It is bent downward (on the low energy side) toward nTe. The downward convex valence band change acts as a potential barrier for holes injected from the p-side electrode 43 into the p-type ZnSe / p-type ZnTe junction.

This problem is caused by the p-type ZnSe contact layer 3
9 and the p-type ZnTe contact layer 41 between the p-type ZnT
This can be solved by providing the e / ZnSe MQW layer 40. This p-type ZnTe / ZnSe MQW layer 4
0 is specifically designed as follows, for example.

FIG. 11 shows the width L _W of the quantum well made of p-type ZnTe in a single quantum well having a structure in which a quantum well layer made of p-type ZnTe is sandwiched by barrier layers made of p-type ZnSe. The results obtained by quantum mechanical calculation for the well-type potential of the finite barrier show how the one quantum level E ₁ changes. However, in this calculation, assuming the effective mass m _{h of} holes in p-type ZnSe and p-type ZnTe as the mass of electrons in the quantum well layer and the barrier layer, 0.6 m ₀ (m ₀ : Static mass) and the well depth is 0.5 eV.

From FIG. 11, the first quantum level E formed in the quantum well is reduced by reducing the width L _W of the quantum well.
It turns out that ₁ can be raised. p-type ZnTe
The / ZnSeMQW layer 40 is designed by utilizing this fact.

In this case, the band bending generated over the width W from the p-type ZnSe / p-type ZnTe interface to the p-type ZnSe side is a quadratic function of the distance x from the p-type ZnSe / p-type ZnTe interface (FIG. 10). φ (x) = φ _T {1- (x / W) ² } (2) Therefore, p-type ZnTe / ZnSeMQW
The layer 40 is designed based on the equation (2) such that the first quantum level E ₁ formed in each of the quantum well layers made of p-type ZnTe is at the top of the valence band of p-type ZnSe and p-type ZnTe. This can be done by stepwise changing L _W so that it matches the energy and is equal to each other.

FIG. 12 shows p-type ZnTe / ZnSeMQW.
A design example of the quantum well width L _w when the width L _B of the p-type ZnSe barrier layer in the layer 40 is 2 nm is shown. In this case, the acceptor concentration N _A of the p-type ZnSe contact layer 39 is 5 × 10 ¹⁷ cm ^−3, and the acceptor concentration N _A of the p-type ZnTe contact layer 41 is 1 × 10 ¹⁹ cm ⁻³ . As shown in FIG. 12, in this case, the total is 7
The width L _w of each quantum well is set from the p-type ZnSe contact layer 39 to the p-type ZnT so that the first quantum level E ₁ thereof matches the Fermi level of p-type ZnSe and p-type ZnTe.
e toward the e contact layer 41, L _w = 0.3 nm, 0.
4 nm, 0.5 nm, 0.6 nm, 0.8 nm, 1.1
nm and 1.7 nm.

Strictly speaking, when designing the width L _w of the quantum well, since the levels of the quantum wells are mutually coupled, it is necessary to consider their interaction. Although the effect of strain due to lattice mismatch between the well layer and the barrier layer must be taken into consideration, it is theoretically possible to set the quantum level of the multiple quantum well flat as shown in FIG.

In FIG. 12, the holes injected into the p-type ZnTe are resonantly tunneled through the first quantum level E ₁ formed in each quantum well of the p-type ZnTe / ZnSe MQW layer 40 to cause p-type ZnSe. Since it can flow to the side, the potential barrier at the p-type ZnSe / p-type ZnTe interface effectively disappears.

As described above, according to this second embodiment,
Similar to the first embodiment, by including the step of interrupting the growth by interrupting the supply of one of the group II element raw material and the group VI element raw material, the acceptor concentration or donor concentration of each layer forming the laser structure can be adjusted. It can be made sufficiently high, which makes it possible to realize a high-performance semiconductor laser capable of emitting light at a short wavelength and having a low threshold current density. More specifically, for example, it is possible to realize a green-emitting semiconductor laser capable of continuous oscillation at room temperature. It is also possible to reduce the applied voltage required for laser oscillation.

The embodiments of the present invention have been specifically described above, but the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the technical idea of the present invention.

For example, in the second embodiment described above, S
The case where the present invention is applied to the manufacture of a semiconductor laser having a CH structure has been described, but the present invention can also be applied to the manufacture of a semiconductor laser having a DH structure (Double Heterostructure).

Further, in the above-mentioned second embodiment, the case where the present invention is applied to the manufacture of the semiconductor laser has been described, but the present invention is applied to the manufacture of the light emitting diode using the II-VI group compound semiconductor. It is also possible to apply it to the manufacture of various semiconductor devices using II-VI group compound semiconductors other than these light emitting elements.

In the first and second embodiments described above, a GaAs substrate is used as the compound semiconductor substrate, and the compound semiconductor substrate is, for example, G
An aP substrate or the like may be used.

[0072]

As described above, according to the present invention,
A p-type or n-type II-VI group compound semiconductor having a sufficiently high acceptor concentration or donor concentration is provided by having a step of interrupting the growth by interrupting the supply of one of the group II element raw material and the group VI element raw material. Can grow.

[Brief description of drawings]

FIG. 1 is a MOCV used in a first embodiment of the present invention.
It is an approximate line figure showing the composition of D device.

FIG. 2 is a sequence diagram for explaining a method for growing p-type ZnSe according to the first embodiment of the present invention.

FIG. 3 is a sectional view illustrating a method of growing p-type ZnSe according to the first embodiment of the present invention.

FIG. 4 is a graph showing an example of measurement results of photoluminescence spectra of a p-type ZnSe layer grown by the p-type ZnSe growth method according to the first embodiment of the present invention.

FIG. 5 is a sequence diagram for explaining a conventional p-type ZnSe growth method.

FIG. 6 is a cross-sectional view for explaining a conventional p-type ZnSe growth method.

FIG. 7 is a graph showing an example of measurement results of photoluminescence spectra of a p-type ZnSe layer grown by a conventional p-type ZnSe growth method.

FIG. 8 is a sectional view of a semiconductor laser manufactured by the method for manufacturing a semiconductor laser according to a second embodiment of the present invention, the cross section being perpendicular to the cavity length direction.

FIG. 9 is a sectional view parallel to the cavity length direction of a semiconductor laser manufactured by the method for manufacturing a semiconductor laser according to the second embodiment of the present invention.

FIG. 10 is an energy band diagram showing a valence band near the p-type ZnSe / p-type ZnTe interface.

FIG. 11 is a graph showing changes in the first quantum level E ₁ of the quantum well with respect to the width L _w of the quantum well made of p-type ZnTe.

FIG. 12 is a schematic diagram showing a design example of a p-type ZnTe / ZnSe MQW layer in a semiconductor laser according to a second embodiment of the present invention.

[Explanation of symbols]

2, 3, 4 Bubbler 5 Reaction tube line 6 Reaction tube 7 Susceptor 8 Substrate 9 Vent line 21 GaAs substrate 23 Adsorption layer of Zn and N 24 ZnSe: N layer 31 n-type GaAs substrate 32 n-type ZnSe buffer layer 33 n-type Zn _1-p Mg _p S _q Se _1-q clad layer 34 n-type ZnSe optical waveguide layer 35 active layer 36 p-type ZnSe optical waveguide layer 37 p-type Zn _1-p Mg _p S _q Se _1-q clad layer 38 p-type ZnS _v Se _1-v layer 39 p-type ZnSe contact layer 40 p-type ZnTe / ZnSe MQW layer 41 p-type ZnTe contact layer 42 insulating layer 43 p-side electrode 44 n-side electrode

Claims (10)

[Claims] 1. A method for growing a II-VI group compound semiconductor, wherein a II-VI group compound semiconductor is grown by a vapor phase growth method using a group II element material, a VI group element material and a dopant. A method for growing a II-VI compound semiconductor, comprising a step of interrupting the growth by interrupting the supply of one of the group II element raw material and the group VI element raw material. 2. The growth is interrupted by maintaining the supply of the raw material of the group II element and the supply of the dopant and interrupting the supply of the raw material of the group VI element. II-VI compound semiconductor growth method. 3. The method according to claim 1, wherein the supply of the raw material of the group VI element and the supply of the dopant are maintained and the growth is interrupted by interrupting the supply of the raw material of the group II element. II-VI compound semiconductor growth method. 4. The supply of only the raw material of the group II element, and then the supply of the raw material of the group II element, and the supply of only the dopant. II-VI compound semiconductor growth method of 5. The method according to claim 1, wherein after the raw material of the group VI element alone is supplied, the feed of the raw material of the group VI element is interrupted and only the dopant is supplied. II-VI compound semiconductor growth method of 6. The VI according to claim 5, wherein the supply of the raw material of the VI group element and the supply of the dopant are not simultaneously performed.
2. The I according to claim 1, wherein a reaction by-product between the group element source material and the dopant is not formed.
Method for growing group I-VI compound semiconductor. 7. The above II by not simultaneously supplying the raw material of the II group element and the dopant.
2. The I according to claim 1, wherein a reaction by-product between the group element source material and the dopant is not formed.
Method for growing group I-VI compound semiconductor. 8. The method for growing a II-VI group compound semiconductor according to claim 2, 4, or 6, wherein the dopant is a p-type dopant containing nitrogen. 9. The method for growing a II-VI group compound semiconductor according to claim 3, 5 or 7, wherein the dopant is a p-type dopant containing lithium or sodium. 10. The II-VI according to claim 1, wherein the vapor phase growth method is a metal organic chemical vapor deposition method or a molecular beam epitaxy method using a gas source. Method for growing group compound semiconductor.