JPH07120818B2 - Light emitting diode - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly to a light emitting diode having a multiple quantum well structure in a light emitting region.

[Conventional technology]

A conventional light emitting diode (hereinafter referred to as an LED) has a structure composed of a pn junction made of the same material, or a single hetero structure or a double hetero structure having a material having a large energy band gap on one side of the pn junction or both sides of the light emitting region. Was realized in. In recent years, as a structure that can further improve the efficiency of radiative recombination in the light emitting region of an LED, a thin layer of a material having a large energy band gap and a material having a small energy band gap is formed in multiple layers in the light emitting region. Sanda, Multi-quantum well structure, Electronics Redders, Vol. 19, No. 6, published March 17, 1983 (Electronics Letters, vol.19,
No.6, 17th March (1983)).

[Problems to be solved by the invention]

An object of the present invention is to provide an LED using a multiple quantum well structure in the light emitting region and having a well width with the highest luminous efficiency.

[Means and Actions for Solving Problems]

Figure 2 shows GaAs / Al _0.3 Ga _0.7 As multiple quantum wells.
Dependence of excitation intensity I _ex on photoluminesence (PL) intensity I _PL in each well width when the width of Al _0.3 Ga _0.7 As, which is the barrier layer, is made constant and the width of GaAs is changed. Is. FIG. 3 shows the dependence of the PL excitation light intensity (I _PL ∝I ^m _ex ), that is, the well width dependence of the slope m (proportional constant in logarithmic representation). It can be seen that the amount of excitation light, that is, the amount of carrier injected into the LED, oscillates between m = 1 and m = 2 depending on the well width. In order to manufacture a multiple quantum well LED with higher luminous efficiency,
It is necessary to manufacture the well width so that the well width is m = 1. The physical image when m = 2 is that the highest energy level (in the conduction band) among the discretely formed levels in the well matches the bottom of the conduction band in the barrier layer. Correspondingly, when m = 1,
This corresponds to the case where the position of the highest energy level in this well is deeper than the bottom of the barrier layer.

〔Example〕

 Hereinafter, examples of the present invention will be described in detail.

FIG. 1 shows the structure of the LED of the present invention. In the figure, (1) is an n-side ohmic contact electrode, (2) is n ⁺
-GaAs substrate, (3) is a n ⁺ -Al _0.3 Ga _0.7 As layer.
(4) and (5) are undoped GaAs and undoped Al _0.3 G
It is a light emitting region of a _0.7 As multiple quantum well, and the thickness of one layer of GaAs is 75 Å within the value of m1 shown in Fig. 3, and one layer of Al _0.3 Ga _0.7 As which is a barrier layer. The thickness is 300Å. In the LED of this example, a GaAs4 layer and an Al _0.3 Ga _{0.7 As} 5 layer were used. (6) is a p ⁺ -Al _0.3 Ga _0.7 As layer, (7) is p ⁺ -GaAs for ohmic contact, and (8) is a p-side ohmic contact electrode. The LED structure of this example was made by molecular beam epitaxy (MBE). In this LED, the + side of the power supply is connected to the p-side contact electrode,
One side of the power source is connected to the n-side contact electrode to emit light in the multiple quantum well region, and the light 10 is extracted from the light extraction window (9). The ohmic contact p ⁺ -GaAs under the window region (9) is of course removed by etching for extraction.

The light output of this LED was 1.5 mW at a drive current of 50 mA.
With this value, we were able to obtain about 1.5 times the output of the same structure without optimizing the width of the well.

〔The invention's effect〕

According to the present invention, a multi-quantum well type LED can be manufactured with a well width having the highest luminous efficiency, and there is a great effect that the LED can be driven at a lower current.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of a multiple quantum well LED, and FIG.
The figure shows the relationship between the amount of excitation light and the emission intensity in PL,
FIG. 3 is a diagram showing the relationship between the well width and the well width and the gradient coefficient of the dependence of the emission intensity on the amount of excitation light. 1 ... n side electrode, 2 ... n ⁺ -GaAs substrate, 3 ... n ⁺ -GaAl
As, 4 ... Undoped GaAlAs barrier, 5 ... Undoped
GaAs well, 6 ... p ⁺ -GaAlAs, 7 ... p ⁺ -GaAs, 8 ...
… P-side electrode, 9 …… Light extraction window, 10 …… Emitted light.

Front page continued (72) Inventor Yoshifumi Katayama 1-280 Higashi Koigakubo, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Yasuhiro Shiraki 1-280 Higashi Koigakubo, Kokubunji City, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Yoshimasa Murayama 1-280 Higashi Koigakubo, Kokubunji City, Tokyo Metropolitan Research Laboratories, Hitachi, Ltd.

Claims (2)

[Claims] 1. A multi-quantum well light emitting diode comprising:
A light emitting diode characterized in that the position of the highest energy level of discrete levels formed in the well has a well width that does not coincide with the bottom of the conduction band of the barrier layer. 2. In a multiple quantum well type light emitting diode,
The light emission according to claim 1, wherein the well width is provided so that the highest discrete energy level formed in the well is near the bottom of the conduction band of the quantum well. diode.