Influence of Carrier Lifetime, Transit Time, and Operation Voltages on the Photoresponse of Visible-Blind AlGaN Metal-Semiconductor-Metal Photodetectors

J. Schlegel1, M. Brendel2, M. Martens1, A. Knigge2, J. Rass1, S. Einfeldt2, F. Brunner2, M. Weyers2, and M. Kneissl1,2

Published in:

Jpn. J. Appl. Phys., vol. 52, no. 08JF01 (2013).

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We investigated the influence of lifetime and transit time of photogenerated carriers on the performance of visible-blind Al0.25Ga0.75N metal-semiconductor-metal photodetectors by a combination of experimental studies and numerical simulations. Good agreement between simulated and measured current-voltage (I-V) characteristics was achieved for several geometries of the interdigitated contact structure. Simulations of the external quantum efficiency (EQE) at low bias voltages showed that a long hole lifetime in the AlGaN absorption layer significantly influences the EQE due to the slow carrier transit in weak electric fields. At 1 V the EQE can be enhanced by a factor of 3 by increasing the hole lifetime from 10 ps to 1 ns. Reducing the electrode spacing from 10 to 1 µm as well as operating the device at higher voltages additionally increases the ratio between carrier lifetime and transit time, resulting in an enhancement of the EQE at a fixed carrier lifetime by one order of magnitude.

1 Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany