Bi2Te3 photoconductive detector under weak light

Bi2Te3 − xSex photoconductive detectors are attractive due to their linear photo-response (LPR), potential in ultrabroadband photo-detection, and compatibility with CMOS technology. However, as a fundamental issue for photo-detectors, the weak-light photo-response of Bi2Te3 − xSex detectors was covered by the bolometric response, the photo-thermoelectric effect, and the 300 K background black-body radiation from the optical window. Here, using a window-less system, we systematically measure the weak-light photo-response of a Bi2Te3 photoconductive detector. The bolometric response and photo-thermoelectric effect are carefully excluded. It shows that LPR can persist to a small light power density of P < 10−8 W/cm2. Meanwhile, the response is maximized at ∼80 K temperature. We suggest that the LPR is rooted in the unique carrier recombination configuration of Bi2Te3, which can result in a constant lifetime for light-generated carriers. The concerned trap level is manifested by a negative photo-response under reduced light intensity. The signature of surface state related signal is presented as a photo-response with the maximum at ∼10 K temperature, which is fragile under increased light intensity. Although the window-less photo-response measurement is at its early stage, it provides a perspective which is different from that of the traditional optical-window based measurement.