Preparation And Mechanism Of Ge Whiskers On SiC Substrate By LPCVD Method

Due to the wide bandgap of SiC-based photoelectric can be only driven by ultraviolet(UV) light and is transparent to infrared light and visible light, this makes it difficult to develop non ultraviolet light controlled SiC power devices. Therefore, SiC/Ge heterojunction can be used as non ultraviolet absorption unit of SiC based light control device. This paper uses LPCVD (low pressure chemical vapor deposition) method in 4H-SiC (0001) substrate Si surface growth of Ge whisker, focusing on process parameters (growth temperature, growth time, source gas flow ratio) effect on the quality of the surface morphology and crystallization,and were characterized and analyzed the morphology and crystalline orientation of Ge whiskers and SiC/Ge interface by SEM, XRD, Raman and TEM methods. The main conclusions are as follows:1. Ge whisker with preferred orientation was successfully prepared on 4H-SiC (0001)substrate Si surface by LPCVD method. Ge nucleus particle have preferential orientation,and the preferred orientation is <111>.The nucleation size is about 9.05nm when the growth temperature of 850? the flow rates of H2 and GeH4 are 200SCCM and 20SCCM,and when the growth time is 60min.2. The nucleation mechanism and growth model of nucleation were analyzed, including the Ostwald annexation effect and S-K growth model during growth process. Under appropriate growth conditions, the thickness of 2D layer was about 7.5nm.3. The effect of growth teperature and source gas flow rate on the morphology of Ge whiskers was investigated. The high growth temperature is beneficial to the growth of longer Ge whiskers, the length of can reach 16?m when 925 ?; the higher GeH4 flow rate,the larger the whisker diameter. Changing the GeH4 flow rate can increase the whisker diameter from 1.3 ?m to 2.6 ?m.