Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 85: Poster Session II

HL 85.128: Poster

Donnerstag, 17. März 2011, 18:00–21:00, P4

Performance characteristic of GaN, InGaN and AlGaN based UV photodetectors with Ti/Al/Mo/Au-contacts — •Bertram Jaeger¹, Jessica Schlegel¹, Patrick Vogt¹, Michael Kneissl^1,2, Sylvia Hagedorn², Veit Hoffmann², Sven Einfeldt², and Markus Weyers² — ¹Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin, Germany — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany

We have investigated UV photodetectors with Ti/Al/Mo/Au-contacts on GaN, Al_0.2Ga_0.8N, In_0.07Ga_0.93N and In_0.11Ga_0.89N respectively by photocurrent spectroscopy, transmission spectroscopy and I-V measurements. The influence of the different absorber materials on contact properties and device performance will be discussed. The spectral response of each detector has a cut-off wavelength according to the bandgap energy of its absorber material between 317 nm and 416 nm. The AlGaN detector has very low dark current in pA-range for an applied bias up to 100 V indicating a Schottky-like character of the contacts (MSM detector). The GaN and InGaN based detectors however show the behavior of photoconductors with ohmic contacts resulting in dark currents in the mA-range for biases of a few volts. The photocurrent of those detectors is sublinear with incident optical power, which hints at the presence of an internal gain mechanism and may explain the observed high currents. The photocurrent of the AlGaN-based detector is below 1 nA up to 100 V bias and linear with optical power.