Novel III‐nitride based transparent photodetectors for standing wave interferometry

The concept of a standing wave (SW) interferometer has been extensively investigated for the last decade. A key problem within these efforts is the development of a transparent ultra-thin photodetector for sampling the intensity profile of the generated SW. We report on the simulation and fabrication as well as on the structural and optoelectronical characterization of highly transparent AlGaN/GaN double-heterostructure and InGaN metal–semiconductor–metal photodetectors based on intraband and band-to-band transitions, respectively. Both detectors have a 20 nm thick optically active layer designed for the light absorption at the wavelength of ∼633 nm. Besides good structural properties of both Al0.35Ga0.65N/GaN and In0.56Ga0.44N structures, the absorbance of the InGaN-based detector was found ∼20 times higher compared to the AlGaN/GaN photodetectors. The temporal characteristics of the detectors are limited by both the RC-constant and by the persistent photocurrent effect. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)