Crystal preparing device, crystal preparing method, and crystal

Abstract

In a crystal preparing device, a crucible holds a mixed molten metal containing alkali metal and group III metal. A container has a container space contacting the mixed molten metal and holds a molten alkali metal between the container space and an outside of the container, the molten alkali metal contacting the container space. A gas supply device supplies nitrogen gas to the container space. A heating device heats the crucible to a crystal growth temperature. The crystal preparing device is provided so that a vapor pressure of the alkali metal which evaporates from the molten alkali metal is substantially equal to a vapor pressure of the alkali metal which evaporates from the mixed molten metal.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a crystal preparing device which carries out crystal growth of a group III nitride crystal, and a crystal preparing method which carries out crystal growth of a group III nitride crystal.[0003]2. Description of the Related Art[0004]Most of InGaAlN devices (or group III nitride semiconductor devices) which are currently used as ultraviolet, purple, blue, or green light sources are produced by carrying out crystal growth of a group III nitride crystal on a sapphire or silicone carbide (SiC) substrate by using the MOCVD method (organic metal chemical vapor deposition), the MBE method (molecular beam crystal growth method), etc.[0005]When sapphire and silicone carbide are used as the substrate in this case, the substrate and the group III nitride semiconductor greatly differ in the coefficient of thermal expansion and the grating constant, and many crystal defects will be included in the gro...

AI Technical Summary

Benefits of technology

[0017]According to one aspect of the invention, there is provided an improved crystal preparing device and method in which the above-described problems are eliminated.

[0019]According to one aspect of the invention there is provided a crystal preparing method which stably holds the mixing ratio of an alkali metal and a group III metal at a controlled ratio to produce a group III nitride crystal.

Problems solved by technology

Such crystal defects relate directly to the drawbacks which cause deterioration of the device characteristics, for example, short operating life and heavy operation power in a luminescence device.

A sapphire substrate is an insulator, and taking out electrodes from such a substrate as in the conventional luminescence devices is impossible.

As a result, the area of the semiconductor device becomes large and there is a problem that the semiconductor device must be produced with high cost.

Moreover, if the area of the semiconductor device becomes large, another problem of a curvature of the substrate may arise due to the use of the combination of different materials: the substrate and the group III nitride semiconductor.

Moreover, in the case of the group III nitride semiconductor device produced on the sapphire substrate, performing the chip separation by cleavage is difficult and preparing the resonator end surface needed for a laser diode (LD) is difficult.

Therefore, it is difficult to perform the formation of the resonator end surface and the chip separation at a single process as in the conventional laser diode (LD), which will increase the manufacturing cost due to complication of the processes.

Although it is possible to reduce the amount of crystal defects by using the improved method, the above problems related to the dielectric feature of the sapphire substrate and the difficulty of the cleavage separation still remain.

However, a GaN substrate which has good quality and practical size is not yet realized.

However, the conventional crystal preparing devices which carry out crystal growth of a GaN crystal have a problem that holding the mixing ratio of metal Na and metal Ga in the mixed molten metal at a controlled ratio during the crystal growth of a GaN crystal is difficult.

As a result, it is difficult to maintain the mixing ratio of metal Na and metal Ga in the mixed molten metal at a controlled ratio stably.

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