Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 73: GaN: Preparation and Characterization IV
HL 73.2: Talk
Thursday, March 29, 2012, 09:45–10:00, ER 270
Development of AlxGa1−xN MSM photodetectors — •Moritz Brendel, Andrea Knigge, Sven Einfeldt, Frank Brunner, Arne Knauer, and Markus Weyers — Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik,Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
Photodetectors for the UV spectral region are required to control UV sources, for the usage in UV lithography, disinfection, and also medical applications. Metal semiconductor metal photodetectors (MSM PDs) have a relatively simple layout and can be processed with quick cycle times. This makes them suitable as a tool for the examination of material quality by photocurrent measurements. By varying the Al content x in the AlxGa1−xN absorber layer the cut-off wavelength can be tuned from 365 nm for x=0 to 200 nm for x=1. With rising Al content the epitaxial growth of AlxGa1−xN layers on sapphire with a low defect density becomes increasingly challenging. A higher defect density is often associated with enhanced carrier trapping and thus can influence the experimentally accessible responsivity. Traps are also associated with persistent photoconductivity (PPC) after turning off the illumination source. The capture of excess carriers at defect states in either the bulk material, at interfaces or at the semiconductor surface retards the decay of the photoinduced conductivity corresponding to an enhanced recombination lifetime. In this talk MSM photodetectors with different absorber compositions grown by MOVPE are presented. Spectral responsivity, dark current, and switching behavior are discussed in relation to material properties of the absorber layer.