High-speed InP Double Heterojunction Bipolar Transistor as Room Temperature Terahertz Detector

Compact and fast detectors, for imaging and wireless communication applications, require technology where low-noise amplifiers are integrated with the detector. Such circuits require the use of transistors that have the highest modulation bandwidth, with cutoff frequencies approaching 1 THz. One of the best candidates is indium phosphide bipolar transistor (InP HBT) technology. We report on responsivity of InP double-heterojunction bipolar transistors (DHBTs) and demonstrate that these transistors can be sensitive room temperature terahertz detectors operating in direct detection configuration and in a large frequency range. In this work, the base-emitter junction nonlinearity of the DHBT is used for detection, while the collector is unbiased. The performances of the DHBTs as terahertz detectors for communications, in the passive configuration, was evaluated by studying their output modulation bandwidth. We observe a cut-off frequency for the DHBT close to 10 GHz that is already interesting for high-data rate communications.