JPS6042611B2 - Method for manufacturing GaP green light emitting diode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a GaP green light emitting diode.

GaP green light emitting diodes are usually manufactured by growing two layers, an N layer and a P layer, on an N-type GaP substrate by liquid phase epitaxial growth.

During growth, the N layer is doped with S, Te, etc., and the P layer is doped with Zn as carrier impurities in the growth layer, and furthermore, only the N layer or both the N layer and the P layer are doped with nitrogen, which is the center of light emission. Nitrogen doping involves NH in the carrier gas.
This is done by mixing a small amount of NH in carrier gas
The nitrogen concentration taken into the growth layer is approximately proportional to the nitrogen concentration.
Further, the luminous efficiency of the luminescent lamp increases in proportion to the nitrogen concentration up to about 5×10'° α-0. on the other hand,
Conventionally, NH3 is usually used as a carrier gas, but in this case, as the concentration of NH3 increases, crater-like abnormal growth (protrusions) occurs on the surface of the growth layer, and the presence of these protrusions makes subsequent steps difficult. The maximum nitrogen doping amount in a state where abnormal growth does not occur is approximately 2×10″8CrfL−3.
Therefore, when doping with nitrogen at a high concentration of 5 x 10'' to obtain the maximum luminous efficiency, conventionally it was difficult to fabricate a light emitting diode due to a large number of abnormal growths.The present invention solves this conventional problem. The present invention provides a method for obtaining a light emitting diode with high luminous efficiency by doping nitrogen at a high concentration while keeping the surface of the growth layer smooth.

Embodiments of the present invention will be described below with reference to the drawings. 1st
The figure shows a GaP green light emitting diode manufactured by the method of this example, in which 1 is an N-type GaP substrate, 2 and 3 are an N-type layer and a P-type layer, respectively, which were sequentially formed on the substrate 1 by liquid phase epitaxial growth. be.

As a carrier impurity, 0.5 to 2×10 is added to the N-type layer 2.
""S with a concentration of α-0, and 2 to 5 × 10 in the P-type layer 3
Each layer is doped with Zn at a concentration of 17 cm@-3, and nitrogen as a luminescent center is doped only into the N-type layer 2 or into both the N-type layer 2 and the P-type layer 3.

As is well known, the liquid phase epitaxial growth method used to form the N-type layer 2 and P-type layer 3 involves bringing a Ga melt containing carrier impurities into contact with the substrate 1 in a carrier gas.
However, in the present invention, Ar is used as a carrier gas at this time, especially when nitrogen is added.
The unique feature lies in the choice of gas.

Figure 2 shows the NH3 concentration (mol%) in the carrier gas (112 or Ar) during liquid phase epitaxial growth.
) and the nitrogen concentration doped into the growth layer.
It is shown that the nitrogen concentration is approximately proportional to the NH3 concentration.

According to the experiment, NH in the carrier gas as shown in the figure. Concentration 1%
The nitrogen concentration in the grown layer (nitrogen concentration at the surface of the grown layer when the growth start temperature is 980'C and the growth end temperature is 900C) is approximately S'5 x 1018d-3. This relationship is almost the same whether H2 or N is used as the carrier gas. On the other hand, the luminous efficiency of the diode is approximately S' proportional to the nitrogen concentration in the growth layer.
-3, S is approximately 0.15% (however, the current density is 12.
5A/Clt). Figure 3 shows NH in the carrier gas.
This graph shows the relationship between the 3 concentration and the surface condition of the growth layer (the number of crater-like abnormal growths formed on the surface (per unit area)), and it shows the relationship between the 3 concentration and the surface condition of the growth layer (the number of crater-like abnormal growths formed on the surface (per unit area)).
Craters are formed at an NH3 concentration of about 0.6%, and an extremely large number of crater-like abnormal growths appear on the surface at an NH3 concentration of 1%.

In this state, subsequent steps (electrode formation, scribing, etc.) are almost impossible. The maximum nitrogen concentration in a usable state is about 3.times.10.sup.18 ar1-3, which corresponds to a luminous efficiency of the diode of 0.07 to 0.09%. On the other hand, when using Ar gas as a carrier gas (curve B in the same figure)
NH3 is difficult to form when using H2.
Even at a concentration of about 1.0%, a substantially flat surface of the grown layer can be obtained. At this time, the nitrogen concentration doped into the epitaxial layer is approximately 5×1018c! rl-3, and the luminous efficiency of the diode is about 0.15% (current density 12.1-2). As is clear from the above, the use of Ar as a carrier gas during liquid phase epitaxial growth is extremely advantageous for performing high concentration nitrogen doping, and the crater-like shape that tends to occur when conventionally H2 is used as a carrier gas There is almost no abnormal growth, and a highly nitrogen-doped epitaxial layer with a smooth surface of the grown layer can be obtained.

As a result, a GaP green light emitting diode with high luminous efficiency can be stably obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a light emitting diode manufactured according to an example of the present invention, FIG. 2 is a diagram showing the relationship between the NFI3 concentration in the carrier gas and the nitrogen concentration in the epitaxially grown layer, and FIG. FIG. 3 is a diagram showing the relationship between NH3 concentration and crater density on the surface of an epitaxial growth layer. 1...Substrate, 2...N-type layer, 3...
...P-type layer.

Claims (1)

[Claims] 1 N as a carrier gas during liquid phase epitaxial growth
GaP characterized by using Ar gas containing H_3
Method of manufacturing green light emitting diode.