Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 85: Poster Session II

HL 85.129: Poster

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

Influence of the interdigitated contact geometry on the performance of Al_0.2Ga_0.8N based MSM photodetectors — •Alexander Wolf¹, Jessica Schlegel¹, Patrick Vogt¹, Sylvia Hagedorn², Sven Einfeldt², Markus Weyers², and Michael Kneissl^1,2 — ¹Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin

The device properties of metal-semiconductor-metal (MSM) photodetectors strongly depend on the interdigitated finger contact geometry. In order to optimize these parameters for visible-blind UV detectors we have characterized Al_0.2Ga_0.8N MSM structures with Ti/Al/Mo/Au Schottky-contacts in varying finger geometries. We have analyzed the device properties by photocurrent spectroscopy and I-V measurements. The detectors have a cut-off wavelength of 315 nm. All structures show dark currents below 3 pA for bias voltages up to 100 V and linearity with optical power. Photocurrents up to 0.9 nA at 310 nm and a maximum responsivity of 57 mA/W at 310 nm and a bias voltage of 100 V have been obtained. For fixed bias voltages a smaller finger spacing leads to a higher responsivity due to the higher electric fields and reduced carrier transit times. The finger width is a crucial parameter for the optimization of the external quantum efficiency due to shadowing of the underlying semiconductor absorber layer. The dependence of the device properties on geometrical parameters of the interdigitated finger contacts will be presented and compared.