Suppressing the Dark Current in Ge MSM Photodetectors Achievable with Thermal Oxidation/Passivation Techniques

• Main Authors: Cheng-ChunChung, 鍾承竣
• Other Authors: Ricky-Wenkuei Chuang
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/29821190825866926640

碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 98 === In this thesis, metal-semiconductor-metal (MSM) infrared photodetectors (PDs) with light absorption taken place in the Ge substrate were fabricated and tested. Due to its low bandgap, many defects are typically present in the surface, which is one of primary reasons for observing a much larger dark current from the fabricated Ge MSM photodetector as compared to other semiconductors-based PDs. In order to reduce the numbers of interfacial and bulk defects, the combined methods of dry oxidation and plasma-enhanced chemical vapor deposition (PECVD) were used to separately deposit different passivation films on the Ge substrates and the performance evaluations were followed thereafter as the metal-insulator-semiconductor (MIS) capacitors and photodetectors were fabricated. The measurement results including the hysteresis observed from the MIS capacitors would later demonstrate that the aforementioned passivation technique effectively suppresses the magnitude of dark current associated with the Ge MSM PDs. Quantitatively, the lowest dark current obtained was on the average of ~7.5x10-8A and the best photo to dark current ratio of 435 was achieved as result of passivating the foregoing PDs on N-type Ge substrates with the dry oxide and PECVD-deposited SiO2 multilayer films.