JPS599983A - Manufacture of gallium phosphide green light emitting diode - Google Patents

Abstract

PURPOSE:To obtain an LED having high luminance, by laminating a plurality of N layers on an N type GaP substrate by a liquid phase epitaxial method with a rest period being provided, introducing N2 in a gaseous phase into the melt at a final stage, providing an N layer, and laminating a P layer. CONSTITUTION:GaP polycrystal and N type impurities are mixed in a Ga melt, and the melt is kept at a temperature of 1,030 deg.C. The surface of a substrate is wetted at a time A. A minute amount of Si is added to the melt. At a time B, H2S with high concentration is flowed for a short time. The temperature is decreased at a low speed. Growing 12 of an N layer is performed at a concentration 2 that is higher than the concentration 1 of the substrate. Then N layer growing 14 is performed with the rest period of 45-120min being provided during the growth. Since the rest period (with constant temperature being kept) is provided, the N layer, whose impurity concentration is gradually lowered in correspondence with the decrease in dislocation density, is obtained. Finally, in the N type growth layer 14, Si3N4 is deposited by NH3 and Si in the melt. The Si in the melt is decreased to 1/4-1/10. An N layer, wherein the concentration 4 of the N2 is about 10<16>cm<-3>, which is very low, is formed. At a time D, Zn is introduced, and a P layer growth at a high concentration 5 is performed. In this constitution, an LED, which has high emitting efficiency and a long life, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a high-brightness gallium phosphide green light emitting diode. It is known that it is good to lower the n-layer concentration of a Pn junction, and for example, according to JP-A-56-24985, if the n-layer concentration is simply lowered, the hue will be on the yellow side (because a large amount of nitrogen is mixed in). Therefore, as shown in Fig. 1(b)K, the n-layer growth is divided into six stages (c)4, and ammonia is added only to the second layer. Introducing (c) nMl near the p-n junction among the low concentration nm (g) (34) in Figure (a).
Although some claim that it is better not to add nitrogen to c34), after repeated experiments, we found that the lifetime and luminous efficiency are not affected by the nitrogen near the p-n junction, but rather by the nitrogen near the p-n junction. It was determined that nitrogen contributes to high luminous efficiency, and that the crystallinity from the n-substrate to the pn junction and other impurities affect the lifetime and luminous efficiency.

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

Figure 2 is a temperature process diagram of liquid phase epitaxial growth of a gallium phosphide green light emitting diode of the wood-based FIA example.
The figure shows the impurity concentration distribution diagram of the green light emitting diode formed by this process. First, GaP polycrystals and n-type impurities are mixed into the Ga melt to create a melt, which is held separately from the semiconductor substrate and then held at high temperature. do. After holding at 1030"C for a while, at time point (3), the melt is placed on the semiconductor substrate to wet the substrate surface, and then heated at 2 to 65°C per minute.
The temperature is lowered to perform epitaxial growth at 75 balls, and the substrate boat is made into a plate shape to reduce the melt thickness to 2. I J1J
It is preferable that the height be 2.8 to 2.8 mm, and that the upper part be provided with a slatted lid so that the melt is in contact with the atmosphere.

If the thickness of the melt is thin as mentioned above, the growth layer tends to become thinner, but if the pn junction is moved away from the substrate, the life will be longer, so the GaP polycrystal to be added to the melt should be at least 4.0% by weight. If the saturated table >cl is maintained, the length can be increased in a short time.A small amount of silicon is added to the melt prior to epitaxial growth, and hydrogen sulfide gas is added to 5.0% at the cooling point FB). The impurity concentration of the melt is increased by flowing it into the atmosphere at a high temperature for a short period of time. Then, the temperature is lowered at a low rate and the impurity concentration of the substrate (1
5 to 10"!l ) (2) N-layer growth is performed at a concentration of 5 to 8ylO'5 which is higher than (1). After that, the n layer is grown with a pause period of 45 to 120 minutes in epitaxial growth.
Layer growth u31 is performed, and finally, n-layer growth ([IO] is performed in an ammonia gas atmosphere (C). Providing a pause time (i.e., constant temperature holding time) lowers the dislocation density in the crystal, but at the same time Since the impurity concentration therein also decreases, n-layers with progressively lower impurity concentrations can be obtained.

In particular, in the final n-layer growth [14], ammonia gas and Si in the melt react to precipitate 5isNn, etc., and the Si in the melt can be substantially removed to 1/4 to 1 d. Therefore, nitrogen is included, but 1 o + 6
An n layer with an extremely low impurity concentration (4) of approximately s is formed.

Thereafter, at time point (D), zinc is introduced into the melt to grow a P layer. Such a P layer is 0.8 to 1.7 X 1
(]Can be controlled by high impurity concentration of crn-3 (5),
If the concentration is too high, the crystallinity will be destroyed and light absorption will occur, so it is not preferable.
If there is a concentration difference of up to 'rnc'rn -3, the lifetime will be shortened or switching operation will occur, but as mentioned above, it is possible to form multiple n-layers while adjusting the crystallinity (especially lattice matching and dislocation in areas with concentration differences). By forming the Si impurity near the pn junction and reducing the Si impurity, switching operation does not occur.
It was possible to obtain a luminous efficiency of 0.45%, which is much higher than 0.45%), and a long-life device that lasted more than 1,500 hours (high temperature and large current test) before the luminance decreased by 80%. Furthermore, by providing a high impurity concentration layer immediately after the substrate.

The above-mentioned crystallinity is more stable and well-ordered, and the melt thickness is thinner, so the epitaxial growth thickness on a single substrate becomes approximately uniform, which facilitates post-processes such as attaching electrodes and improves productivity. Thus, the present invention includes a first step of bringing a melt into contact with an n-type gallium phosphide substrate, epitaxially growing a plurality of n-layers while providing a rest period, and finally introducing nitrogen into the melt from the gas phase. A gallium phosphide green light-emitting diode with stable crystallinity, high luminous efficiency, and long life because it includes the second step of epitaxially growing the n-layer and the sixth step of epitaxially growing the p-layer to form a pn junction. can be manufactured.

[Brief explanation of drawings]

Figure 1 is an impurity concentration distribution diagram of a conventional light emitting diode (a
) and temperature process diagram (b), Figure 2 is a temperature process diagram of liquid phase epiaxial growth of a gallium phosphide green light-emitting diode according to an example of the present invention, and Figure 6 shows the impurity concentration of the green light-emitting diode formed thereby. It is a distribution map.

Claims (1)

[Claims] 1) The first step is to bring the melt into contact with an n-type gallium phosphide substrate, then epitaxially grow multiple n-layers while providing a rest period, and finally introduce nitrogen into the melt from the gas phase to grow the n-layers. a second step of epitaxial growth; and a sixth step of epitaxial growth of the p layer to form a pn junction.
A method for manufacturing a gallium phosphide green light emitting diode, characterized by comprising the steps of