Measurement and simulation of top- and bottom-illuminated solar-blind AlGaN metal-semiconductor-metal photodetectors with high external quantum efficiencies
M. Brendel, M. Helbling, A. Knigge, F. Brunner and M. Weyers
Published in:
J. Appl. Phys., vol. 118, no. 244504 (2015).
Abstract:
A comprehensive study on top- and bottom-illuminated Al0.5Ga0.5N/AlN metal-semiconductormetal (MSM) photodetectors having different AlGaN absorber layer thickness is presented. The measured external quantum efficiency (EQE) shows pronounced threshold and saturation behavior as a function of applied bias voltage up to 50V reaching about 50% for 0.1 µm and 67% for 0.5 µm thick absorber layers under bottom illumination. All experimental findings are in very good accordance with two-dimensional drift-diffusion modeling results. By taking into account macroscopic polarization effects in the hexagonal metal-polar þc-plane AlGaN/AlN heterostructures, new insights into the general device functionality of AlGaN-based MSM photodetectors are obtained. The observed threshold/saturation behavior is caused by a bias-dependent extraction of photoexcited holes from the Al0.5Ga0.5N/AlN interface. While present under bottom illumination for any AlGaN layer thickness, under top illumination this mechanism influences the EQE-bias characteristics only for thin layers.
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
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