III-nitride terahertz photodetectors for the Reststrahlen gap of intersubband optoelectronics

We report the development of terahertz intersubband photodetectors based on GaN/AlGaN quantum wells, covering the frequency range that is fundamentally inaccessible to existing III-V semiconductor devices due to Reststrahlen absorption. Two different approaches have been employed to mitigate the deleterious effects of the intrinsic polarization fields of nitride heterostructures: the use of suitably designed double-step quantum wells, and epitaxial growth on semipolar GaN substrates. Promising results are obtained with both approaches, which could be extended to other device applications as a way to utilize the intrinsic advantages of nitride semiconductors for THz intersubband optoelectronics.