Effects of P-Type Layer and Transparent Conducting Oxides Film on Ge-on-Si Photodetector

• Main Authors: Lu-Tzu Liu, 劉律慈
• Other Authors: Jenq-Yang Chang
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/8vczvc

碩士 === 國立中央大學 === 光電科學與工程學系 === 104 === In recent decades, near-infrared-region photodetector has attracted attention gradually with development of fiber-optical communication. Germanium-on-Silicon photodetector not only can detect NIR light but also contain the advantages of low cost and easy integration. However, the defects due to the heterojunction between Si and Ge would increase the dark current which causes power consumption and signal interference so decreasing the dark current of a Ge-on-Si photodetector becomes an important issue. In this study, we fabricated different p-type layer of a photodetector and investigated its effect. In addition, we employed Indium Tin Oxide (ITO) thin film on a photodetector to lower the dark current. The photodetectors fabricated in this research are p-i-n structure. At the beginning, we used Reduced-Pressure Chemical Vapor Deposition (RPCVD) to deposit intrinsic germanium (i-Ge) on n-type silicon substrate. Then, different kinds of p-type layer were grown by RPCVD and Electron Cyclotron Resonance Chemical Vapor Deposition (ECRCVD). The results revealed that photodetector with p+-Ge layer grown by ECRCVD exhibited higher responsivity of 0.171 A/W than others. The reason is due to the stronger built-in electric field caused by heavier doping concentration in p-type layer. On the other hand, we grew different characteristic ITO thin film by controlling the process parameters in Radio Frequency (RF) Sputtering system, argon flow, oxygen flow and ambient pressure. Also, we employed these ITO thin films on photodetector to lower the dark current and investigate on the relationship between them. Here, we have demonstrated a Ge-on-Si photodetector with ITO layer and its performance is dark current of 0.12 μA at -3 V bias, dark current density of 0.048 mA/cm2.