| Summary: | 碩士 === 國立中央大學 === 光電科學與工程學系 === 103 === The particular metal-germanium-metal photodetector (PD) is investigated in this research. Germanium has good absorption coefficient in near infrared such as 850nm, 1310nm and 1550nm which are commonly used in optics communication. Unfortunately, the prohibitive cost of germanium wafer makes it difficult to popularize. Radio frequency (RF) sputtering system is used to deposit single crystal intrinsic germanium film to fabricate the photodetector. It not only keeps performance of Ge but also reduces the cost more than a factor of five.
In this investigation, interdigitated electrodes are used on the devices with the purposes of a relative easy process for high-speed devices and a comparable process for the integrated circuit. Three different substrates are used to fabricate photodetectors including n-Si, p-Ge and i-Ge/n-Si. Responsivities and frequency responses are measured and analyzed. Besides, the effect of the Ge thin film on the device was also discussed. The responsivity of PDs are 0.46A/W, 0.257A/W and 2.71mA/W for n-Si, p-Ge and i-Ge/n-Si respectively. The frequency response can be achieved 43.35MHz for Si-based MSM PD.
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