Bias-Polarity-Dependent Photocurrent Spectra of Terahertz Stepped-Quantum-Well Photodetectors

Abstract

The authors study the photoresponse of a broadband THz-frequency detector with stepped quantum wells in the absorption layer. Due to the asymmetric distribution of the wave function of the second excited subband ${E}_{2}$, the escape probability for photoexcited electrons is strongly dependent on bias polarity, which is responsible for the different shapes of photocurrent spectra under positive and negative bias voltages. These results show that not only band structure but also the nature of the wave function itself plays a key role in designing these high-performance quantum-well photodetectors.