AlxGa1-xN for solar-blind UV detectors

There has been a growing interest in the development of solar-blind, ultrav iolet (UV) photodetectors for use in a variety of applications, including e arly missile threat warning, flame monitoring, UV radiation monitoring and chemical/biological reagent detection. The AlxGa1-xN material system has em erged as the most promising approach for such devices. However. the control of the material quality and the device technology are still rather immatur e. We report on the metalorganic chemical vapor deposition of high quality AlGaN thin films on sapphire substrates over a wide range of Al concentrati ons. The quality of these AlGaN materials was verified through a demonstrat ion of high performance visible and solar-blind UV p-i-n photodiodes with p eak cutoff wavelengths ranging from 227 to 364 nm. External quantum efficie ncies for these devices reached as high as 69% with over five orders reject ion ratio from the peak to visible wavelengths. For the development of UV p hotodiode arrays. back illuminated photodiodes were also fabricated and mea sured. External quantum efficiencies of up to 15% were achieved with reject ion ratios greater than four orders of magnitude, demonstrating the feasibi lity of AlGaN, solar-blind devices for use in photodetector array applicati ons. (C) 2001 Elsevier Science B.V. All rights reserved.