It has been expected that silicon carbide (SiC) is applied to a high frequency electric power device, a high temperature device and an optoelectronics device, and its investigation for actual use is now underway. The p-electrode for the SiC device, i.e. an ohmic electrode for p-type SiC is generally formed of TiAl composed of titanium (Ti) and aluminum (Al) (see JP-A-5-13812).
Generally, in many cases, the device needs an ohmic electrode. However, in the device using compound semiconductor, generally, an ohmic contact between a semiconductor layer and an electrode cannot be obtained without being subjected to heat treatment. Only provision of a metallic layer exhibits a Schottky barrier. The ohmic contact formed by the heat treatment provides greatly different contact resistances according to a semiconductor material, an electrode material, a heat treatment temperature, a heat treatment time, etc.
TiAl, which is presently expected as a material for a low resistance ohmic contact, can provides very low resistance. However, in order to realize such low resistance, heat treatment at a high temperature for a long time as well as a large amount of Al is required. This leads to the problems of deterioration of a device function, a device life, etc. due to deterioration of surface morphology and thermal damage for a semiconductor crystal layer.
This invention has been accomplished in order to attain the above problems, and an object of this invention is to provide an electrode for p-type SiC which can provide improved surface morphology and less thermal damage for a semiconductor crystal layer due to formation of an electrode.
USPTO Backgrounds
USPTO Backgrounds