CdTe nBn photodetectors with ZnTe barrier layer grown on InSb substrates

Abstract

We have demonstrated an 820 nm cutoff CdTe nBn photodetector with ZnTe barrier layer grown on an InSb substrate. At room temperature, under a bias of −0.1 V, the photodetector shows Johnson and shot noise limited specific detectivity (D*) of 3 × 1013 cm Hz1/2/W at a wavelength of 800 nm and 2 × 1012 cm Hz1/2/W at 200 nm. The D* is optimized by using a top contact design of ITO/undoped-CdTe. This device not only possesses nBn advantageous characteristics, such as generation-recombination dark current suppression and voltage-bias-addressed two-color photodetection, but also offers features including responsivity enhancements by deep-depletion and by using a heterostructure ZnTe barrier layer. In addition, this device provides a platform to study nBn device physics at room temperature, which will help us to understand more sophisticated properties of infrared nBn photodetectors that may possess a large band-to-band tunneling current at a high voltage bias, because this current is greatly suppressed in the large-bandgap CdTe nBn photodetector.