JPH01175278A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To improve the crystalline property of a p-type clad layer and extend its lifetime characteristics, by causing the carrier concentration of the p-type clad layer adjacent to an active layer to come to a low level in an AlGaInP semiconductor laser. CONSTITUTION:In the case of an AlGaInP semiconductor laser 12, the carrier concentration of a p-type clad layer in a double hetero structure is set below 6X10<17>cm<-3>. In other words, an MOCVD process allows an n-type (Al0.5Ga0.5)0.5 In0.5P clad layer 3, an undopped Ga0.5In0.5P active layer 4, a p-type (Al0.5Ga0.5)0.5 In0.5P clad layer 11 where positive hole concentration is 2X10<17>cm<-3>, and a p-type GaAs cap layer 6 to grow one after another on an n-type GaAs substrate 2. Required ions are implanted in such a way that the ions reaches the p-type AlGaInP clad layer 11 by leaving the center part of the cap layer 6 in a stripe form and the semiconductor laser 12 is made up by forming an ion-implanted high resistance layer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to semiconductor lasers, particularly to AI Ga1nP-based semiconductor lasers.

[Summary of the invention]

The present invention improves lifetime characteristics in an A I Ga1nP semiconductor laser by lowering the carrier concentration in the p-type cladding layer adjacent to the active layer.

[Prior Art] In recent years, there has been an increasing demand for visible light semiconductor lasers as light sources for optical discs, laser printers, bar code readers, and the like. As this type of semiconductor laser, an A I Gaunt'-based semiconductor laser that is lattice-matched on a GaAs substrate is attracting attention. This Q1! In the Ga1nP semi-dedicated laser, the active layer contains (A 1 y Ga + - y ) o, 5
1no, 5P (0≦y<1), and the cladding layer has a wider nominal gap than the active layer.
It is constructed using L, s summer no, 5P (0x≦1).

FIG. 5 shows an example of a conventional A I Ga1nP semiconductor laser. This semiconductor laser ([) is made of n-GaAs
n-(Gao, s)6.5 was deposited on the substrate (2) by the MOCVD (metal organic chemical vapor deposition) method.
lno, sP cladding layer (3), undoped Gas,
51rlo, sP active layer (4), carrier (hole)
p-(^e6,5 G
ao, s)o, sIn+, sP cladding layer (5) and p-GaAs cap layer (6) are grown one after another, and then the central part of the cap layer (6) is left in a stripe shape and p
-AI Ga1nP cladding layer (constructed by implanting required ions to reach 51 to form an ion-implanted high resistance layer (7). (8) and (9) are n-GaA
The electrodes formed on the back surface of the s-substrate (2) and the surface of the cap layer (7) are shown.

[Problem that the invention seeks to solve]

In the conventional AI Ga1nP semiconductor laser described above, the p-AI Ga InP layer 1 used as the cladding layer
51! ;! , carrier mobility is small 10-20
cm''/v-sec, therefore, in order to lower the resistance, a carrier concentration as high as lXl0'''ell-' has been used. Although this laser achieved continuous oscillation at room temperature, its lifespan was short and it deteriorated rapidly, making it impossible to put it to practical use.

In view of the above-mentioned points, the present invention provides a highly reliable visible light semiconductor laser having a life characteristic sufficient for practical use.

[Means for solving problems]

The present invention is applied to an AI Ga1nP semiconductor laser) in which the carrier concentration of the p-type raft layer in the double heterostructure is 6 x 10I? Configure by setting it to cII-s or lower.

[For production]

p-type cladding layer, i.e. p-type (A 1 xGa+-x)
o-5Ino, , Looking at the relationship between the carrier (hole) concentration in the p cladding layer and its p-type impurity concentration and the flow rate of the p-type dopant raw material supplied during growth, the p-type impurity concentration tends to be saturated even at a high flow rate. However, a saturation tendency can be seen from the flow rate where the carrier concentration increases. The carrier concentration at which saturation begins varies depending on the value of A/Mi component X, but the flow rate at which saturation begins is the same.

For example, if the composition X is 0.5, the carrier concentration is 6×
A tendency towards saturation can be seen from about 1017CI. In the carrier concentration saturation region, the emission intensity decreases rapidly. This is because defects are formed due to excessive impurity atoms and the crystallinity is reduced. On the other hand (AI M Ga+-x
) o, slr+++, , p As for the composition of the cladding layer, A1&[I x = 0.4 is considered to be the lower limit that can be used in practical use.

In the present invention, by setting the carrier concentration of the p-type cladding layer to 5 x 10" (Jll-3 or less), which does not cause a decrease in crystallinity, the formation of defects that cause deterioration of life can be suppressed, and the life characteristics can be dramatically improved. improved.

〔Example〕

Hereinafter, embodiments of a half R41E laser according to the present invention will be described with reference to the drawings.

The curve (+) in Fig. 2 shows the Zn-doped p(A e @, 5Gao,
s) shows the relationship between the hole concentration of o, sIn+, and spa and the flow rate of DMZ (dimethyl zinc), a p-type dopant raw material, supplied during growth. In the low flow area of the DMZ, the concentration of authentic tags increases in proportion to the flow rate, but 5XI
A tendency towards concentration saturation can be seen from about Q"cm-'.

The curve in Figure 2 ([[) is p (A 1 o, 5Ga
o, s) o, 5Inn, s SIMS in P layer
(Secondary Ion MassSpec
D? of Zn1 degree measured by LromeLry)? I
This shows Z flow dependence. It is recognized that the Zn concentration does not show a tendency to saturate even in the high flow rate region of DMZ.

Figure 3 shows p(A lo, sGa*, s) @,
5lno, sP layer chamber? This figure shows the dependence of the peak intensity of light emission near the band edge of photoluminescence at ff1 (300K) on the concentration of the authentic tag. In the hole concentration saturation region seen in the curve (1) of FIG. 2 above, the emission peak intensity decreases rapidly, indicating that the crystallinity decreases. This is considered to be due to the formation of defects related to excessive Zn atoms. In an actual laser device, if such a defect exists in the cladding layer near the active layer, it becomes a light absorption center, and non-radiative recombination of carriers occurs, thereby causing the defect to multiply. Injected carriers are trapped in the defects generated in the cladding layer, resulting in a decrease in carrier injection efficiency into the active layer and an increase in threshold voltage m1th.

Furthermore, even if defects move into the active layer due to an electric field, light, etc., the luminous efficiency may decrease, the threshold current may increase, and deterioration may occur.

In the present invention, the hole concentration in the p-type cladding layer is set to a low concentration that does not cause deterioration of crystallinity, thereby suppressing the formation of defects that cause lifetime deterioration, and improving laser lifetime. The density of this genuine bill is (AJX Ga+-x). , 51n. , 5P(0
In the p-type cladding layer of <x≦1) system, it is related to the 81 composition X, and when the 81 composition must be done. In addition, when the AlIJI composition is smaller than 0.5, for example, when it is 0.4, which is the practical limit, the density of the original card should be set to 6X10I? C11-3 or below. Furthermore, when the 1Mi composition is greater than 0.5, the Zn acceptor level becomes deeper, so the hole concentration needs to be lowered. For example, when the AI group composition is 1.0, the hole concentration becomes lower. Reduce the concentration to 2XIQ"cjIA-3 or less.

FIG. 1 shows an embodiment of a semiconductor laser according to the present invention.

The basic structure of the semiconductor laser sub-layer of this example is the same as that shown in FIG. 5 described above, but in particular, the original concentration of the p-type cladding layer OD is set to 2×10''(J-').

That is, n-(81o, sGao, s)o, 5l was deposited on the n-GaAs substrate (2) by the MOCVD method.
no, sP cladding layer (3), undoped Gao,
s[no, sP activity N(4), hole concentration 2X10''
(J-3 p (Affio, 5 Gao, s)
a, 5lno, sP cladding layer 00 and p-GaAs camp layer (6) are grown sequentially, and then the central part of the camp layer (6) is left in a stripe shape as required to reach the p-^eGalnP cladding Iou. ions are implanted to form an ion-implanted high resistance layer (7), thereby constructing a half-four-body laser 0δ. (8) and (9) are respectively n-G'aAs substrates (
The electrodes formed on the back surface of 2) and the surface of the cap layer (7) are shown.

Figure 4 is ^j! Double heterostructure of Ga1nP system (D
H') 50'll of semiconductor laser: p-type (^lx Ga+-x) o, s In with average lifetime in life test
* indicates the dependence on DMZ flow rate during growth of the sP cladding layer.

In the figure, (al is tb+, t in the case of the embodiment shown in FIG.
c), fdl is when the 81 composition X is 0.7. As is clear from this figure, D? By lowering the lZ flow rate, the lifetime can be dramatically increased. For example, in (a) (the embodiment shown in FIG. 1), a visible light semiconductor laser that can be used in practical use for about 5000 hours can be obtained.

〔Effect of the invention〕

According to the present invention, in an AlGa1nP semiconductor laser, by setting the carrier concentration of the p-type cladding layer adjacent to the active layer to 6 XIO"am-3 or less, the crystallinity of the p-type cladding layer is improved and the lifetime characteristics are improved. Therefore, it is possible to provide a highly reliable visible light semiconductor laser having a lifespan that can withstand practical use.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of a semiconductor laser according to the present invention, and FIG. 2 is a (A1 o, 5Gao, s) o, sl
Figure 3 is a graph showing the DMZ flow rate dependence of the regular plate concentration and Zn concentration of n+, 5pJ1.
, s) o, 5lno, sP layer at room temperature A graph showing the dependence of the luminescence peak intensity near the band edge of the photoluminescence at room temperature, Figure 4 is the A I Ga1nP
FIG. 5 is a graph showing dependence of I) MZ flow rate during growth of a p-type cladding layer of average life in a 50° C. life test of a system DH semiconductor laser, and FIG. 5 is a configuration diagram of a conventional semiconductor laser. (2) is n, -GaAs substrate, (3) is n-type cladding layer, (4) is active layer, +51 (Ill is p-type cladding layer, (6) is camp layer, (7) is ion implanted high resistance layer,
+81 +91 are electrodes. Proceedings of the same Hidemori Matsukuma February 18, 1988 Patent Application No. 332385 3, Relationship with the case of the person making the amendment Address of the patent author: 6-7-35, Kitashina-yo, Part-time Ward, Tokyo Issue name (2
18) Sony Corporation Representative Director Norio Ohga 4, Agent 6, Number of inventions increased by amendment 7, Subject of amendment Detailed description of the invention in the specification and drawings (1) No. 8 in the specification Page 6 line “Kiya Nobu layer (7)
" is corrected to "cap layer (6)". (2) In the drawings, Figures 1 and 5 are corrected as shown in the attached sheets. Above are the main prize #, the bottom of the bottom of the ditch, Fig. 1, Fig. 5.

Claims (1)

[Claims] In an AlGaInP-based semiconductor laser, the carrier concentration of the p-type cladding layer in the double heterostructure is 6×1.
A semiconductor laser set to 0^1^7cm^-^3 or less.