Analysis on high speed response of a uni-traveling-carrier double hetero-junction phototransistor**Project supported by the National Natural Science Foundation of China (Grant No. 61006044), the Natural Science Foundation of Beijing, China (Grant Nos. 4122014 and 4142007), and the Fund from the Beijing Municipal Education Committee, China (Grant No. KM200910005001).

Abstract

In this paper, the positive influence of a uni-traveling-carrier (UTC) structure to ease the contract between the responsivity and working speed of the InP-based double hetero-junction phototransistor (DHPT) is illustrated in detail. Different results under electrical bias, optical bias or combined electrical and optical bias are analyzed for an excellent UTC-DHPT performance. The results show that when the UTC-DHPT operates at three-terminal (3T) working mode with combined electrical bias and optical bias in base, it keeps a high optical responsivity of 34.72 A/W and the highest optical transition frequency of 120 GHz. The current gain of the 3T UTC-DHPT under 1.55-μm light illuminations reaches 62 dB. This indicates that the combined base electrical bias and optical bias of 3T UTC-DHPT can make sure that the UTC-DHPT provides high optical current gain and high optical transition frequency simultaneously.