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Si-based Metal-Germanium-metal Photodetector

Posted on:2009-04-29Degree:MasterType:Thesis
Country:ChinaCandidate:Z M CaiFull Text:PDF
GTID:2178360272491079Subject:Condensed matter physics
Abstract/Summary:PDF Full Text Request
Development of photodetectors operating at 1.3-1.6μm wavelength, with high response speed, high quantum efficiency and low dark current, are not only the need for optical communication, but also the need for silicon-based optoelectronic integration.Ⅲ-Ⅴsemiconductor materials have larger absorption coefficient in the 1.3~1.55μm, However,Ⅲ-Ⅴsemiconductor materials are too much expensive, and their thermal conductivity properties and mechanical properties are poor. In addition, they are not compatible with the existing mature silicon-based technology, which limits its application in the integrated optoelectronics. SiGe material is compatible with the existing mature silicon technology. Furthermore, the absorption wavelength of strained Ge has expanded to 1.6μm. In this paper, Si-based metal-semiconductor-metal(MSM) photodetectors and SOI-basedResonant-cavity-enhanced(RCE) MSM photodetectors for 1.3~1.6μm operation are fabricated.(1) Tensily strianed Ge thin films are successfully grown on Si and SOI substrates with a combination of low temperature SiGe and Ge buffer layers by UHV-CVD. High crystal quality, low dislocation density and low roghness of the Ge layer are characterized.(2) The influence of parameters on the performance of MSM photodetectors including quantum efficiency, wavelength selectivity is theoretically studied in details. The parameters such as reflectivity of the front and rear mirrors, absorption length are optimized to obtain high quantum efficiency.(3) The processes and the key technologies for fabricating Ge photodetectors are investingated. The conditions related to photolithography and various parameters of ICP are optimized. MSM Ge photodetector and RCE-MSM Ge photodetector have been successfully fabricated.(4) Electrical performance and spectral response of the devices are measured. Relatively small dark current has been obtained for both types of the photodetectors. The responsivity of the Si-based Ge MSM photodetectors and SOI-based RCE-MSM photodectors are 1.45mA/W and 0.63mA/W at 1.55μm for reverse bias of 8V, respectively. The resonant effect can also be observed.
Keywords/Search Tags:Ge, MSM photodetector, resonant cavity
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