JPS59208888A - Compound semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To enable to improve the luminous efficiency by a method wherein a layer whose P type impurity concentration is lower than that of a P type clad layer and forbidden band width is more than that of an active layer and less than that of said clad layer is provided between said clad layer and said active layer. CONSTITUTION:An N<-> layer should have an impurity concentration smaller than those of the N and P layers at approx. one-tenth. Besides, for example, a thin barrier layer 15 of the thickness of 200Angstrom having a large forbidden band width and an N type small impurity concentration is sandwiched between the N type active layer 14 and the P type clad layer 16. Carriers are enclosed in the N type active layer 14, and the P type impurity causing a non light emitting recombination center is distant from the active layer 14. Therefore, the luminous efficiency of the active layer 14 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser or a light emitting diode (LE).
This relates to the structure of a compound semiconductor light emitting device such as D).

Semiconductor lasers or LEDs are usually made using GaAs as a substrate.
G aAj? A s/n −G aA s .

Or P-InP/InGa using InP as a substrate
It has a double heterojunction structure such as AsP/InP. Here, the capital letters P and N represent the impurity type of the layer having a wide forbidden band width, and the lower case letters p and n represent the impurity type of the layer having a narrow forbidden band width. At this time, the injected carriers are formed in a narrow forbidden band called the active layer.
or InGaAsP layer, and emit light by recombining and emitting light. At this time, zinc (Zn), cadmium (ED), etc. are usually used as the P-type doping impurity. However, these P-type impurities are GaA/As
or InP, the P-GaA/As layer or P-
This significantly deteriorates the luminous efficiency of the InP layer. According to the authors' experiments, Zn was added to InP by Ixio ('+1
Doping reduced the photoluminescence efficiency to about one-tenth of that without doping. This phenomenon occurs because the Zn used as an acceptor moves within the crystal, creating defects in the lattice where group II atoms should exist, and these defects become non-radiative recombination centers. This is thought to be due to the fact that it no longer works as an inclusive acceptor. When a P-type cladding layer containing many such non-radiative recombination centers is in contact with an active layer, many of the injected carriers confined in the active layer undergo non-radiative recombination near the interface between the P-type cladding layer and the active layer. This causes a decrease in luminous efficiency.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to improve the luminous efficiency of compound semiconductor light emitting devices such as semiconductor lasers and LEDs.

According to the present invention, a narrow band gap is formed on a semiconductor crystal substrate between a layer that is N-type and has a wide bandgap (N-type cladding layer) and a layer that is P-type and has a wide bandgap (P-type cladding layer). In a semiconductor light emitting device having a double heterojunction structure having a light emitting layer (active layer) having a band width, there is a gap between the P type cladding and the active layer, where the P type impurity concentration is lower than that of the P type cladding layer, and a forbidden band is formed between the P type cladding and the active layer. FIG. 2 is a diagram illustrating the first embodiment of the invention, which includes a layer (barrier layer) whose width is greater than or equal to the forbidden band width of the active layer and less than or equal to the forbidden band width of the P-type cladding layer; (N-,
P-, etc.) indicates that the impurity concentration is about 1/10 as small as that of N and P. In this embodiment, an n-type active layer 14
A thin rear layer 15 having a thickness of 200× and having a wide forbidden band width and a small impurity degree of N type is sandwiched between the P type cladding layer 16 and the P type cladding layer 16. 13 is an N-type cladding layer. The carriers are confined in the n-type active layer 14, and the p-type impurities, which cause non-radiative recombination centers, are far from the active layer 14, so the luminous efficiency of the active layer decreases. In this example, the n-type barrier layer 41 is interposed between the n-type active layer 14 and the P-type cladding layer 16, and the luminous efficiency is improved as in the above embodiment.

In the above example, the P-type cladding is Zn doped I
The N-type cladding was S-doped InP.

Further, the n-type active layer was S-doped InGaAsP.

The P or p dopant is not limited to Zn, but CD may be used, and the N or n dopant may be Sn.

In addition to InP and InGaAsP, GaAs +
GaAlAs may also be used. It is clear that the thickness of the barrier layer is not limited to 200X.

In the figure, 13 represents an N-type cladding layer, 14 represents an n-type active layer, 6 represents a P-type cladding layer, and 15.41 represents a barrier layer.

Figure 1 Figure 82

Claims (1)

[Claims] On a semiconductor crystal substrate, an N-type layer with a wide forbidden band width (
A double heterojunction structure with a light-emitting layer (called an active layer) having a narrow bandgap between a P-type layer (called an N-type cladding layer) and a P-type layer with a wide bandgap (called a P-type cladding layer). In the semiconductor light emitting device, a P-type impurity concentration is lower than that of the P-type cladding layer, and a forbidden band width is greater than or equal to the forbidden band width of the active layer, and Pg is provided between the P-type cladding layer and the active layer.
A compound semiconductor light emitting device characterized by having an N (or n) type semiconductor layer (referred to as a barrier layer) whose width is equal to or less than the forbidden band width of a cladding layer.