Top- and bottom-illumination of solar-blind AlGaN metal-semiconductor-metal photodetectors
phys. stat. sol. (a), vol. 212, no. 5, pp. 1021-1028 (2015).
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The spectral performance of solar-blind AlxGa1-xN based metal-semiconductor-metal ultra-violet photodetectors has been measured for top- as well as bottom-illumination at different bias voltages. In the bottom-illumination case the external quantum efficiency spectra can be tuned between a peak or a broad wavelength spectrum by adjusting absorber layer thickness and applied bias voltage. For thin absorber layers the external quantum efficiency is enhanced by a factor of three, reaching 20% quantum efficiency at 20V bias, compared to the front-illumination case. Results of twodimensional device simulations are well in agreement with the experimental findings. From these simulations it can be concluded, that the different spectral response for top- and bottom-illumination results from the different overlap of optical carrier generation by absorption and carrier transport by the electric field. Spectra of external quantum efficiency of solar-blind metal-semiconductor-metal photodetectors upon top-illumination (dashed) and bottom-illumination (continuous) at 1 V, 5 V, and 20V bias voltage. The Al0.5Ga0.5N absorber layers of different thickness dAbs were grown on AlN/sapphire templates.
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, D-12489 Berlin, Germany
AlGaN, device simulations, metal-semiconductor-metal structures, solar-blind photodetectors.