P-Si/n-SiC Heterojunction And Photoelectric Effect

Silicon carbide (SiC) has attracted much attention for power device applications due to its excellent physical properties, wide band gap, high thermal conductivity and high saturated drift velocity. However, because of the wide band-gap, SiC is not sensitive to the long-wave length lights ranging from visible to infrared region of the optical spectrum. This essentially limits its application for detection of visible and infrared light. A promising way to solve this problem is to adopt a Si/SiC heterojunction diode.In this work, we discuss how to growth Si epilayers on 6H-SiC substrates and control the doping concentrations of the p-Si films. Then the relation of the different doping concentrations and heterojunction characteristics was studied. In order to increase the optoelectronic, different metal sputtering on substrate and forming ohmic contactSi films is hetero-epitaxially grown on Si face of (0001) n-type 6H-SiC substrates by LPCVD (Low Pressure Chemical Vapor Deposition), and B2H6 is used as a dopant for the p-Si grown at temperatures in a range of 800-950℃. The sheet resistance adjusted from 1.33×105Ω/口to 35Ω/口with the B2H6 and SiH4 ratios varies from 1/12000～17/900. Optoelectric response test results of the heterojunction samples indicate that low doping concentration of the Si epilayer induces large photocurrent. The photocurrent density is 10mA/cm2 when the sheet resistance of the Si layer is 2000Ω/口. As the sheet resistance of the Si epilayer decreases to 20Ω/口, the photocurrent density accordingly reduces to 0.01mA/cm2. We use PIN heterojunction to increase photocurrent. Compare with pn heterojunction, the photocurrent of PIN structure increase to 24mA/cm2...