High speed, low noise ultraviolet photodetectors based on GaN p-i-n and AlGaN(p)-GaN(i)-GaN(n)structures
- 13 October 1997
- journal article
- research article
- Published by AIP Publishing in Applied Physics Letters
- Vol. 71 (15), 2154-2156
- https://doi.org/10.1063/1.119366
Abstract
We have investigated the spectral response of front-surface-illuminated GaN and AlGaN/GaN ultraviolet photodetectors prepared by reactive molecular beam epitaxy on sapphire substrates. GaN homojunction photodiodes exhibited a peaked response near the band edge. This enhanced response was absent in the AlGaN/GaN heterojunction detectors. We analyzed the effect of -layer thickness of the GaN diodes on the magnitude of the peak photoresponse. The AlGaN/GaN photodiodes had a maximum zero-bias responsivity of 0.12 A/W at 364 nm, which decreased by more than 3 orders of magnitude for wavelengths longer than 390 nm. A reverse bias of −10 V raised the responsivity to 0.15 A/W without any significant increase in noise. The root-mean-square noise current in a 1 Hz bandwidth is ∼1.0 pA, corresponding to a noise-equivalent-power of ∼8.3 pW. We measured extremely fast decay times of 12 ns for the AlGaN/GaN and 29 ns for the GaN photodiodes.
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