JPS6019156B2 - Manufacturing method of light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a light emitting device, and more particularly to an improved method for manufacturing a P-type liquid phase growth layer in a GaP light emitting device.

In the production of Gap's light emitting devices, liquid phase growth using a Ga solution is widely used as the GaP epitaxial growth method, and Zn is often used as the P-type impurity because it allows easy control of acceptors. ing.

However, green LEDs have a serious drawback in that when oxygen mixes near the PN junction surface, Zn-○ close pairs are formed and red light is emitted. Zn also has the disadvantage that it is difficult to control in a relatively low concentration region.
The present invention improves the drawbacks of the conventional methods, and provides a method in which C is used as a P-type impurity in Ga milk, and the C is added from the gas phase. Next, the present invention will be explained in detail with reference to examples.

Fig. 1 is a perspective view of a sliding type liquid phase growth apparatus, in which 1 is a boat section mainly made of graphite in the shape of a plate, and a recess 2 for storing a semiconductor substrate is formed on the top surface of the boat section. The inner surface of the recess is covered with a quartz layer. Next, reference numeral 3 denotes a sliding plate made of graphite, the lower surface of which is in contact with the upper surface of the boat part in a liquid-tight manner, and has a melt reservoir 4 containing a through hole in the bottom opposite to the above-mentioned recess. Furthermore, the inner surface of the melt reservoir is also coated with a quartz layer in the same manner as the recess of the boat part.
Next, the liquid phase growth process performed by the above-mentioned apparatus is carried out in the second stage.
This will be explained with reference to FIGS.

First, in FIG. 2, there is a gap in the recess 2 of the boat part 1.
The wafer 10 is stored and heated, and GaP is deposited in the melt reservoir 4 of the sliding plate 3.
After adding the melt 20, the sliding plate is slid in the direction of the arrow. In the state shown in FIG. 3 in which the recess and the through hole at the bottom of the melt reservoir are aligned, the liquid phase growth layer 10' is exposed on the GaP wafer, resulting in the state shown in FIG. 4. For example, the state in Figure 2 is 1000.
The temperature is raised to 0.00 C, the temperature is changed to the state shown in FIG. 3, and then to the state shown in FIG.
During this slow cooling, various impurities can be added to the gallium solution and added to the growth layer. In the case of a green light emitting element (hereinafter abbreviated as LED), an N-type Gap wafer is used to
In the state shown in FIG. 4, the quartz is slowly cooled to 97,000 ℃ in an atmosphere for 2 days, whereby quartz is reduced and added to Si and Ga to grow an N-type first epitaxial layer. At the stage when this growth is achieved, the carrier gas is switched to Ar, and NH3 and C are added thereto, and the temperature is maintained at a constant temperature for a while, and N and C are added to the Ga. By further cooling slowly, a P-type second epitaxial layer to which N and C are added is grown. Note that at this time, Si in Ga reacts with N and is removed from Ga. Furthermore, Zn was added from the gas phase,
Gradually, a third epitaxial layer of P type with a size of 2 x 1 pi 7-skin 3 or more grows. In this way, three N-P-P epitaxial growth layers are formed from the crystal side of the substrate. In order to increase the luminous efficiency when the wafer grown in this way is made into a device with a side aperture of about 0.3, the concentration of the second epitaxial layer doped with nitrogen as a luminescent center must be lower than that of the first epitaxial layer. It is known that it is important to make the concentration sufficiently lower than the concentration of the layer. The inventors have discovered that the concentration of P-type impurities in the second epitaxial layer can be sufficiently controlled by adjusting the amount added to the carrier gas during growth. As an example, the relationship between the P-type impurity concentration when the second epitaxial layer is grown from 970q○ is shown in the fifth column.
As shown in the figure. The horizontal axis of the figure is the concentration of CH4 (%), and the vertical axis is the concentration of CH4 (%).
The solid line shows these correlations for the impurity concentration (one block) of the epitaxial layer. Also, in the figure, the axis is shared with the above, and the vertical axis shows the luminous efficiency G (%) and the correlation therebetween with the broken line. Regarding the figure, for example, if the CH4 concentration in the carrier gas is 0.13%, the concentration of the second epitaxial layer can be controlled to 3 to 6 x 1 to 6 (low-3). The concentration of the first epitaxial layer is generally 3-5×1pi7(
It can be seen that the concentration of the second epitaxial layer is ideal. Furthermore, although the concentration of the P-type layer varies depending on the reaction apparatus used for epitaxial growth, the impurity concentration can be controlled by slightly correcting the concentration of the C ratio depending on the apparatus. The efficiency was measured by disposing the wafer electrodes formed as described above, dividing them into elements of about 0.3 mm, and applying a current of 2 hA.
A high efficiency of ~0.3% was obtained, whereas conventionally it could not exceed 0.2%, but the effect is extremely remarkable.

0 According to the present invention, acceptor control in a relatively low concentration region, which has been difficult in the past in liquid phase growth, is facilitated by using a carbon-containing gas, which contributes to the mass production of high-brightness green light-emitting devices. It's a huge amount.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the liquid phase growth apparatus, FIGS. 2 to 4 are cross-sectional views for explaining the liquid phase growth process using the liquid phase growth apparatus, and FIG. 5 shows C specific concentration and acceptor concentration, FIG. 3 is a diagram showing the relationship between C specific concentration and luminous efficiency of a light emitting element. 1...Boat part (of sliding type liquid phase growth apparatus), 2
・・・・・・Concave part of boat part, 3... Sliding plate, 4・
... Fuji liquid reservoir on the sliding plate, 10 ... Gap wafer, 10' ... Liquid phase growth layer, 20 ... GaP
Chick liquid. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. In manufacturing a GaP light emitting device in which a liquid phase growth layer is formed by adding carbon as the main P-type impurity using a liquid phase growth method, the atmosphere during liquid phase growth contains a gas that can liberate carbon. A method for manufacturing a GaP light emitting device, which comprises adding carbon generated by thermal decomposition to a liquid phase growth layer.