JPS59163821A - Liquid phase epitaxial growth - Google Patents

Abstract

PURPOSE:To facilitate to control concentration of electrons when a III-V group compound semiconductor layer is to be formed by a method wherein the compound of Te and another element is used as the N type impurities of the III-V group compound semiconductor. CONSTITUTION:When a III-V group compound semiconductor is to be manufactured according to liquid phase epitaxial growth, a compositionally uniform compound of Te and another element is used as N type impurities. As the other element, at least one kind of elements to act as N type impurities to exert no adverse effect to the characteristic of the element, or to act as electrically neutral impurities is used. As the element thereof, Al, Ga, In, Si, Sn, Pb, As, Sb, Bi and Se are used. Te is used generally as N type impurities at liquid phase epitaxial growth of the III-V group compound semiconductor, while because the segragation factor of Te is large, the charge quantity thereof becomes extremely small, and precision of weighing is deteriorated. By using the compound of the other impurity and Te, enhancement of weighing precision can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to liquid phase epitaxial growth suitable for precisely controlling the electron concentration of a ■-■ group compound semiconductor layer, particularly an n-type layer.

[Prior art]

Conventionally, n-type nr −
In order to obtain a V group compound semiconductor layer, S is mainly used as an impurity.
Elements of n or Ille were used (e.g., RIXE, Nahory et al., AI).
pI.

1'hys, J7ft, 27.562~564,
1975 i S, N, G.

Chuctal, Appl, Phy, Le
ft, 38.766-768゜1981; M,
ll1rao et at, J, Appl, P
hys, 51°453'l-4540, 1980;P
, Kordos et al., AppLPhys
, Left, 34.366-368.1979;
RXA, Logan et al., J. App.
l, phyS, 50.5970-5977, 1979
).

On the contrary, in the case of Sn, the segregation coefficient in the crystal is small, so high electron concentration (e.g. 5 x 10"Crn-3 or more) is required.
It is not suitable as an impurity to obtain In addition, because the above segregation coefficient is small, the content of Sn in the solution for silicon growth becomes large, but at this time, the crystallization composition of the main component elements of the ■-V group changes greatly due to the change in the above content of Sn. There are drawbacks. For the above reasons, Te has generally been used as an n-type impurity in liquid phase epitaxial growth of the 111-V group. However, in the liquid phase growth of m-v group compound semiconductors, the segregation coefficient of Te is very high, and therefore the amount of Te charged is very small (for example, in the Ga A tA-s system, I
The amount of Te charged to obtain an electron concentration of
The accuracy of measuring Te was poor, and the control of electron concentration in the n-type epitaxial crystal layer was insufficient.

[Purpose of the invention]

The purpose of the present invention is to control the electron concentration of an n-type epitaxial crystal layer with good reproducibility by improving the weighing accuracy of a trace amount of Te used as an n-type impurity, and to improve the liquid phase related to improving the reproducibility of device characteristics. The goal is to provide epitaxial growth.

[Summary of the invention]

In order to achieve the above object, the present invention uses a compositionally uniform compound of Te and other elements. As the other element, at least one element selected from the group consisting of elements that serve as n-type impurities or electrically neutral impurities that do not adversely affect device characteristics was selected. Representative examples of this element group are listed below. A A , Oa + I n+
S' r S ” r P b IAs+ Sb
, It i and Se.

[Embodiments of the invention]

Figure 1 shows a suitable light source for an optical disk pickup.
x MC8P (Mad If ied Chanel
FIG. 2 is a cross-sectional view of a semiconductor laser of the ed 5ubstra teplaner type. When performing liquid phase epitaxial multilayer growth for the purpose of producing such a semiconductor stack, Te and Qa are used as n-type impurity raw materials in weight ratio]:
The key point of the present invention is to use a compositionally uniform alloy having an IQO of about 500 to 1:IQO. For example, the first layer 1
Type 1 cladding J*0at-xAAxAs (X=0.45
) as the solution composition for the purpose of obtaining () ” 8 g
, At 8.9 mg.

For 200 mg of QaAs, the above 'peHQa=1+5
00 alloy 30mJ7 to 1:100 alloy 160m
g, and set the Te concentration of the n-cladding layer to 3×
1017cW! -3 to 3 x 1018Crn-3 to improve the controllability and reproducibility of the Te concentration. In this case, Te is diluted 100 to 500 times, and therefore the weighing accuracy of ql e can be improved by two orders of magnitude, and 'I' in n-GaAtAs of the semiconductor laser fabricated using the present invention can be improved by two orders of magnitude.
It was possible to control ef11 degrees with good reproducibility. In addition,
Except for the types of impurities, this is the same as the prior art, so details will be omitted. Similar results were also obtained when a compound of the above elements other than Qa and Te was used.

Incidentally, crystal growth and wafer processing other than those related to the present invention were performed by conventional methods.

In FIG. 1, 1 is an n-GaA3 substrate, and 2 is an n-GaA3 substrate.
GaAtAs cladding layer, 3 is GaAtAs active layer, 4 is p-GaAtAs cladding layer, 5 is n-GaA
6 is a Zn diffusion region, 7 is an n-side electrode, and 8 is an n-side electrode.

Conventionally, many longitudinal single mode semiconductor lasers are unsuitable as light sources for optical disks due to changes in ambient temperature.
Mode competition noise caused by simultaneous oscillation of multiple longitudinal modes has been a problem. However, this problem is caused by the electron density (ND
1017cm-3) and the ratio (P, (%)) of the optical output existing in the semiconductor layer out of the total optical output of the laser, ND-Fn≧500 (1) The solution is to do this. 1st
In order to satisfy α) in the device shown in the figure, there is a method of changing the thickness of the active layer, but the thickness of the active layer has a correlation with the maximum optical output of transverse fundamental mode oscillation and the lifetime characteristics of the device. It is set to ±0.01 μm. Therefore,
In order to satisfy (1), it is necessary to increase ND, but doping a large amount of n-type impurities tends to cause problems in device characteristics such as an increase in threshold current density and lifetime characteristics. For the above reasons, the doping amount of the n-type impurity is set to Nn-7', 550 to minimize the necessary minimum amount. 1st
In the device structure shown in the figure, n and p type Qai-xk
X of LXA8 cladding layer is 0.45, active layer thickness is 0.07
When ±0.01 μm, No −7' n = 550
Let amg be the Te preparation song determined by . n-type impurity Te
For 10 wafers obtained by AMG weighing using conventional Te alone, the yield of low-noise devices among 50 devices arbitrarily selected from each wafer showed large variations between wafers, as shown in Figure 2. , the overall yield was also not sufficient. According to the present invention, since the weighing accuracy of Te can be greatly improved, as shown in FIG. 3, there is an effect of improving the wafer-to-wafer variation in the yield of non-defective devices and the overall yield using the same evaluation method. Note that the noise characteristic evaluation of the semiconductor laser was performed using a laser output of 3 rn W and a measurement frequency of 2.
-12 MHz with a measurement bandwidth of 300 KHz.

Furthermore, the same effect can be obtained by using At, In, Si, Sn, Pb, ASIsb, BI, Se, or the like as an element that creates an alloy with a uniform composition with Te.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a semiconductor laser device, FIG. 2 is a diagram showing changes in the yield of low-noise devices obtained by the conventional method between wafers and lots, and FIG. 3 is a diagram showing how the yield of low-noise devices is obtained using the present invention. FIG. 3 is a diagram showing changes in yield between wafers and lots. 1 ・-n-(]aA8 substrate, 2・=n-GaAtAs
Cladding layer, 3...(UaAtAs active layer, 4...
p-GaAtAS cladding layer, n-Ga1l cap layer, 6...7. n diffusion region, 7...n side electrode,
・N-side electrode. Agent Patent Attorney Akio Takahashi

Claims (1)

[Claims] 1. As the n-type impurity of the III-V compound semiconductor, T
e and at least one element selected from the group consisting of another element that becomes an n-type impurity or an element that becomes an electrically neutral impurity in the semiconductor crystal. Characteristic liquid phase epitaxial growth method. 2. A, /, Ga as an element forming the above group. (n, Si, sn, pb, As, sb, Bi. 3e). 3. The liquid phase epitaxial growth method according to claim 1, characterized in that the above m-v group compound semiconductor is selected from Gar -x A
A patent application characterized in that tz As (0≦X≦1)