There has been a growing interest for the development of solar blind ultraviolet (UV) photodetectors for use in a variety of applications, including early missile threat warning, flame monitoring, UV radiation monitoring and chemical/biological reagent detection. The Al_xGa_1-xN material system has emerged as the most promising approach for such devices. However, the control of the material quality and the device technology are still rather immature. We report here the metalorganic chemical vapor deposition, the n-type and the p-type doping of high quality Al_xGa^1-xN thin films on sapphire substrates over a wide range of Al concentration. The quality of this Al_xGa_1-xN material was verified through the demonstration of high performance visible and solar blind ultraviolet p-i-n photodiodes with a cut-off wavelength continuously tunable from 227 to 365 nm, internal quantum efficiencies up to 86% when operated in photovoltaic mode, and a ultraviolet-to-visible rejection ratio as high as six orders of magnitude. Both front and back side illuminated p-i-n photodiodes were realized. Photodetector devices were also demonstrated on GaN material obtained using lateral epitaxial overgrowth. The technology for such Al_xGa_1-xN based devices was improved in an effort to enhance their performance, including the development of ohmic metal contacts to both n-type and p-type Al_xGa_1-xN films with an Al concentration up to 40%.

Date Published: 12 June 2001
PDF: 11 pages
Proc. SPIE 4288, Photodetectors: Materials and Devices VI, (12 June 2001); doi: 10.1117/12.429409

Published in SPIE Proceedings Vol. 4288:
Photodetectors: Materials and Devices VI
Gail J. Brown; Manijeh Razeghi, Editor(s)