The Fabrication Of Au/4H-SiC Semitransparent Schottky UV Photodiode

Silicon carbide is a promising wide bandgap semiconductor material for high-temperature, high-power, high-frequency and anti-radiation device applications because of its wide bandgap(about ), high critical electric field( ), large saturation electron drift velocity and superior thermal conductivity ( ). Due to the wide bandgap( >3eV ), ultraviolet photodetectors based on 4H-SiC can be used to detect UV light in the background with strong visible light3. 3eV3MV /cm5W /K?cm or infrared ray. Recently, there are some research on metal/4H-SiC contact ,but few reports are focused on Au/4H-SiC schottky photodiode. And there are few reports on Au/4H-SiC semi-transparent schottky photodiode. In most reports, the metal used to form schottky contact is thick relatively, which will cause much reflection and absorption loss, and result in the small transmittance. Thereby, it is significant to have a research on semi-transparent schottky contact which has great effect on enhancing the UV detectivity of the photodiode.In this article, the process such as RCA Cleaning, magnetron sputtering, lift-off, oxidation and etching were used. Magnetron sputtering was used to deposit thin Au on the front side of 4H-SiC to form semitransparent Schottky contact and alloys Ti,Au were used to form ohmic contact on the n+ backside.The the I-V,C-V characteristics and spectrum response characteristics of the device have been measured and analyzed. The photosensitive area of the device is 200μm×200μm. As deposited, the dark current of device is 1.05×10-12A at zero bias and 1.32×10-11A at -30V. After annealing, the dark current of device is less than 1 pA. The forward turn-on voltage is 0.75V and the breakdown voltage is 190V.As deposited, the Schottky barrier height of 4H-SiC Schottky contact is 1.75eV .After annealing, the Schottky barrier height is 2.0eV. The range of spectrum response is 200-400nm, the peak wavelength is 290nm. At room temperature, as deposited the largest quantum efficiency of the device is 36.0% and 36.6% after annealing when the reverse voltage is 20V.