InAs這種材料由於本身擁有超快的電子遷移率且截止頻率可以到達3.4μm，因此非常適合應用於遠紅外線波長的超高速光檢測器。然而，之前的應用都是製作於導電的InAs基板上，這樣會產生一個巨大的寄生電容，而且會限制光檢測器的速度表現。此外，在室溫操作下會有嚴重的表面態和暗電流產生。因此，在這篇論文中我們展示了一個成長在半絕緣基板(GaAs)上的InAs高速光檢測器，而且利用鋅擴散的方式來降低漏電流。在室溫和低偏壓(-0.2V)操作下，這個新穎的光檢測器3-dB頻寬可以達到20GHz，且擁有合理的暗電流密度(11A/cm2)。InAs is an attractive material system for fabricating high-speed photodiodes in far-infrared wavelengths due to its extremely high electron mobility and a cut-off frequency as long as around 3.4μm. However, the reported InAs PD is usually grown on the conductive InAs substrate, which should result in a significant parasitic capacitance and further limit the speed performance of PD. In addition, the serious surface state and huge leakage current of InAs based PDs at RT operation is usually observed. In this paper, we demonstrated a novel high-speed InAs photodiode (PD), which was grown on semi-insulating (S.I.) GaAs substrate with the Zn-diffusion guard ring to suppress the leakage current. Such novel PD exhibits a 3-dB optical-to-electrical (O-E) bandwidth as wide as 20GHz, a reasonable dark current density (11A/cm2), under a small reverse bias voltage (-0.2V) and RT operation.
