JPS59213179A - Light emitting element - Google Patents

Abstract

PURPOSE:To obtain the titled element whose luminous efficiency is sufficiently excellent as the light source for optical communication even by low current injection type by a method wherein a GaAlAs double hetero type junction is formed by successively laminating a P type GaAlAs clad layer, an N type Ga1-xAlxAs active layer, and an N type GaAlAs clad layer on a P type GaAs substrate. CONSTITUTION:The P type GaAlAs clad layer 2, N type Ga1-xAlxAs active layer 3, and N type GaAlAs clad layer 4 are formed by lamination on the P type GaAs substrate 1. It is sufficient that the value (x) is approx. 0<=x<=0.3 in order that said active layer 3 becomes in direct transition. Besides, the active layer 3 (0<=x<=0.3) should have the growing temperature at 830-829.9 deg.C, cooling speed at 0.1 deg.C/min, and is doped with Si. In case of doping the active layer 3 with Si in such a manner, it is generally known that said layer grows in P type; however, this active layer turns to an N type layer according to the condition of growing temperature and Si doping amount. Further, the light emitting element thus turning the active layer 3 to N type improves about double in the luminous efficiency as compared with the case of said element turned P type.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a light emitting device, and particularly to a semiconductor light emitting device as a light source for optical communication.

[Prior art and its problems]

Since the difference in lattice constant between GaAs and AA'As is small, various device structures of GaAlAs-based double heterojunction type light emitting devices have been prototyped as semiconductor lasers or light emitting diodes.

Furthermore, recently, a light emitting element in which a GaAlAs double heterojunction is formed on a P-type GaAs substrate has been devised.

When a KGaAlAs double heterojunction is formed on this AHP type GaAs substrate, the final layer of crystal growth becomes an N-type layer, and if a donor impurity with a small segregation coefficient such as 11le is used, this N-type 1- donor impurity Once is I
The concentration is as high as about 10''-3, making it very easy to form an N-type ohmic electrode.Therefore, the mass productivity of device formation is greatly improved.

However, from Hiko, germanium, which is a P-type impurity, is often used as an impurity in the active layer of such a double hetero-m junction, that is, the active layer is a P-type layer.
In the case of low-current injection type light-emitting elements, such as light-emitting diodes, the quantum efficiency of light emission is extremely low, which has been a major problem.

[Purpose of the invention]

An object of the present invention is to provide a light-emitting element having sufficiently good luminous efficiency as a light source for optical communications even if it is of a low current injection type.

[Summary of the invention]

The present invention is based on the P-type (+ a , A,
A 13As cladding layer, an N-type Ga 1-xAexAs active layer, and an 8It layer of N-type GaAlAs cladding layer were sequentially formed.
The object of the present invention is to obtain a light emitting element in which a GaAA'As double heterojunction is formed.

〔Effect of the invention〕

G a A I formed on a P-type C+ a A s substrate
A s double heterozygous (Jal-xAlXΔS
By making the active layer N-type, it is possible to obtain a light-emitting element with significantly better luminous efficiency than when the active layer is P-type.

[Embodiments of the invention]

A first embodiment of the present invention will be described with reference to FIG. That is, on the P-type Oa As substrate (1), the P-type Oa
A AlAs cladding layer (2) is laminated, and an N-type OaAlAs cladding layer (211) is formed via a fdN-type Ga1-xAlxAs active layer (3). (4) are formed by laminating them.

Note that in order for this N-type Ga1-xAlxAs active layer (3) to have a direct transition, X may be approximately 0≦X≦0.3.

The characteristics of this light-emitting element, such as a light-emitting diode, are as described above (3a+-xA, gxAs (0≦
X≦0,3) Where the active layer (3) is of N type ((there is).

Next, P m (TaA, s substrate (1
) P-type Oa AIJ A S cladding layer (2), N-type Ga1-xklxks (0≦X≦0
．． 3) The liquid phase growth conditions for the active layer (3), N-type Oa AI A, and s ground layer (4) will be explained. First, P-type Oa
A I A, s cladding layer (2) growth temperature is 833
Ge
is added.

In addition, the N-type layer a+-xAl, which is a feature of this first embodiment,
xAs (0≦X≦0.3) Growth temperature of active layer (3) is 83000 to 829.9°C1 Cooling rate is 0.100
/f+, Si is added and -C is added.

Next, the growth temperature of the N-type GaAlAs cladding layer (4) is 829.9°0 to 826°01, and the cooling rate is o, z0
'1'e is added at 0/e.

It is known that when Si is added to the active layer in this way, the active layer generally grows as a P-type.
It is clear that it will become a type layer.

This is because while investigating the correlation between the amount of 81 added in the active layer and the luminous efficiency, we noticed that there was a large variation in luminous efficiency, and after examining this correlation in detail, we found that the active layer doped with Si is not necessarily This became clear from the fact that it was not always a KP type layer. Furthermore, it has been found that the light-emitting element in which the active layer is made into an N-type in this way has an effective efficiency approximately twice as high as that of a light-emitting element in which the active layer is made into a P-type.

1. As shown in Table 1, active l@St addition,
This is also clear from the relationship between the electrical conductivity type of each active layer, N type or P type, depending on the growth temperature, etc., and the measured values of the relative optical output of these two types of active layers.

Table 1 Note that the instability of crystal growth using different amphoteric impurities as described above is thought to be due to the instability of heteroepitaxy.

Next, a second embodiment of the present invention will be described. The first example of the child chain is N-type (Ja+-xAlxA, s
(0≦X≦0.3) The active layer (3) is
In this second embodiment, '1'e is added instead of Sl. That is, by adding Te, N-type Ga I-
xAl>汰S(0≦X≦0.3) Active j@ is formed, and the amount of addition of the reed l1le or the growth temperature etc. is controlled by controlling the N-type layer a+-xAAxAs (0≦X≦0. 3)
When the carrier concentration of the active layer is ~3 x 10''>, '', a light emitting device with luminous efficiency approximately twice as high as that of the light emitting device with a P-type active layer as in the first example can be obtained. Ta.

Incidentally, the above facts are true for the N-type layer a+-xAlxAs (
0 ≦ This is interpreted as being less susceptible to the effects of recombination at , resulting in high luminous efficiency.

Next, a third embodiment of the present invention will be described with reference to FIG. This third embodiment uses the "jP-type GaA7As cladding layer (2-P-type GaA7As cladding layer) shown in the first and second embodiments described above.
An N-type 0aAs layer (5) for current confinement is partially formed on the S substrate (1).
). The same parts and parts as in Figure 1 are given the same reference numerals. According to this third embodiment, current concentration in the light emitting element is improved, and a light emitting element with higher luminous efficiency can be obtained. It is clear that the first to third embodiments described above are effective not only for low current injection type light emitting elements such as light emitting diodes, but also for light emitting elements such as semiconductor lasers.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the invention, and FIG. 2 is a sectional view showing a third embodiment of the invention. ■...P-type GaAs 2...P-type ()aAlAs cladding layer 3/N-type layer a+
-xAdxAs (0≦x≦0.3)41. N type G
aAlAs crat 44 5...N-type GaAs current confinement layer

Claims (1)

[Claims] (1) P-type GaAlAs on a P W GaAs substrate
Cladding layer, N m Ga+-xAlxAs active layer, N
GaAlAs type cladding layers are sequentially stacked to form GaA1
A light emitting device characterized in that a 3A s double heterojunction is formed. (2) The light emitting device according to claim 1, wherein the N-type Ga + -xAlxAs active layer is doped with Si. (3) N-type Ga 1-xAA! The xAs active layer is made of Te
Claim 1 characterized in that:
The light-emitting element described in . (4) N-type Ga+-xAlxAs activity Jf1 (D x
The light emitting device according to claim 1, wherein: 0≦x≦(), 3. (5) P-type layer a AA! The As cladding layer is partially formed on the P-type layer aAs cladding layer through an N-type layer aAs current confinement layer. Light emitting element.