JPS5918688A - Gallium phosphide light emitting diode - Google Patents

Abstract

PURPOSE:To obtain ohmic contact of an electrode with light absorption being suppressed, by forming a thin P layer, whose impurity concentration is aproximately an order of magnitude higher, on a P layer, which forms a P-N junction, thereby obtaining high light emitting efficiency. CONSTITUTION:N type layers 2-4 are epitaxially grown on an N type GaP substrate 1. In these N type layers, the concentration of the layer 2, which is closest to the substrate 1, is made high, and the impurity concentrations are sequentially decreased. Finally, the layer, whose impurity concentration is 5X 10<16>cm<-3> or less, is grown. Zn doped P type layers 5 and 6 are epitaxially grown on said layer 4, and a P-N junction 7 is formed. In this case, it is convenient to obtain high light emitting efficiency when the impurity concentration difference of an order of magnitude or more is provided in the junction 7. However, the ohmic contact of the electrode cannot be obtained under this state. Therefore, the impurity concentration of the layer 6 is made higher than that of the layer 5 by an order of magnitude. However, since the impurity concentration of the layer 6 is high, light absorption tends to occur. Therefore, it is required that the thickness of the layer 6 is made to be 10mum or less.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a potassium phosphorus-emitting diode that emits high-intensity green light.

Conventional green light-emitting diodes using gallium phosphorus use a melt containing a predetermined amount of impurities in the liquid-phase Echter+Shall growth method, so that the concentration distribution opening shown in Figure 1 is The impurity concentration immediately after the substrate 1a) was the lowest, and the impurity concentration was high in the n layer (b) near the Pn junction Q7). Therefore, the characteristics as a light emitting diode were stable, but the difference in impurity concentration at the pi junction (1η) became small and the luminous efficiency was 0.296 or less.

Therefore, the impurity concentration can be reduced as shown in Fig. 2 (the n-layer tC approaches the p-n junction (27)) by providing a pause time for the physical growth and by interfering with the impurity concentration in the melt using the gas phase. I was able to lower it. However, the second layer 1d) is I
Since the impurity concentration remains high at about Zinc, which contributes to light emission, diffuses into the n-layer, resulting in a tilted junction.Therefore, the light extraction efficiency decreases, and non-radiative recombination centers are generated, resulting in a short lifetime and overall darkness.

The present invention has been made in consideration of the above points, and will be described in detail below based on examples.

FIG. 3 1a) is a schematic diagram of a potassium phosphorous light emitting diode according to an embodiment of the present invention, and FIG. 3 1b) is an impurity concentration distribution diagram thereof. In the figure, (1) is an n-type gallium phosphide substrate pulled and sliced by the Chicorals method, with an impurity concentration of 1 to 3 x 10 ``a!I-''e allo. (2)+3
1 +41 Hasono & Board (N-type layer grown on top of 11, n-type layer (2) closest to the substrate (1)
The impurity concentration is kept high to ensure crystal matching, and the impurity concentration is gradually lowered until C1, where A:, Jtnia is introduced,
0, 5 to 1.2 X I D 16cyt-' (D
Grow an n-type layer (4) with impurity concentration (7). C511
Reference numeral 61 designates a P-type layer also epitaxially grown, and both are doped with zinc as an impurity source contributing to light emission. There are various theories about the impurities that contribute to green light emission, and some say that silicon on the n-side and carbon on the p-side are preferable.
It is thermally unstable. The present invention relies on the theory that general tellurium and zinc are used as levels and nitrogen promotes luminescence. It was found that doping the side with zinc provides the best luminous efficiency and stability. Therefore, the P-type layer (5) has a thickness of 0.5 to t 4 x 10
Although the impurity concentration of α is good, the ohmic of the electrode cannot be maintained as it is, so the impurity concentration is approximately 1X10.
A P-type layer (6) of cm 2 is provided. However, since this P-type layer (61) has a high impurity concentration, it tends to absorb light, so it needs to be 10 μm or less.

By creating the structure as described above, there is an impurity difference of approximately one digit of 71 degrees near the Pn junction (7), and since the high concentration P layer (6) is far away, the difference at the pn junction (7) Good crystallinity, fewer non-radiative recombination centers, and less zinc diffusion. For this reason, the Pn junction (7) maintains a stepped junction, increasing the injection efficiency. As a result, a luminous efficiency of 0.4% could be obtained. Moreover, since there is a thin P-type layer (61) with a high impurity concentration, it was possible to obtain an electrode of λ-3 lac while suppressing light absorption.This effect is more effective as the n-layer concentration near the p-n junction is lower. is large, but the effect is great when the nIm concentration is 5×10”14 or less.

As described above, the present invention includes an n-type gallium phosphorous substrate and a layered substrate having an impurity concentration of 5X1016 cm-5 or more on the surface.
an n-layer, a first p-layer containing zinc laminated on the surface of the n-layer, and an impurity concentration of approximately one order of magnitude lower than that of the first p-layer laminated on the first p-layer with an impurity concentration of iK < 10 μm or less. Since it is a potassium phosphorus emitting diode with a thick second P layer, its characteristics are stable and its brightness is high due to its high luminous efficiency and high light extraction rate.

[Brief explanation of the drawing]

Figures 1 and 2 are impurity concentration distribution diagrams for explaining the characteristics of a light emitting diode, Figure 3 1a) is a schematic diagram of a gallium phosphorous light emitting diode according to an embodiment of the present invention, and +h) of the same figure is its impurity concentration distribution. It is a diagram. In the figure, (1) is a potassium phosphorus substrate, +21 +31
(41 is an n-type layer, C51 (61 is a p-type layer, (7) is a Pn
It is a joining. 1□1 Figure 2 Figure 8 (G) (b)

Claims (1)

[Claims] 1) An n-type potassium phosphorus substrate, an n layer laminated thereon and having a surface impurity concentration of 5xlOas or less, a first P layer containing zinc laminated on the surface of the n layer, and the first two
A potassium phosphorous light emitting diode comprising a second P layer laminated on top of the first P layer and having a thickness of less than 10 μm and having an impurity concentration of approximately one order of magnitude higher than that of the first P layer.