Photo-injected carrier distributions in metal-semiconductor-metal photodetectors imaged by photoluminescence microscopy

The effects of size and transparency of fingers on the spatial distribution of radiative recombination of photoinjected carriers in metal-semiconductor-metal photodiodes have been investigated using photoluminescence microscopy. Investigations of detectors having fingers and spaces of 20 μm showed a depletion region width which varies with bias voltage in a quasi-one-dimensional Schottky diode functional form. Regions of non-uniform electric field were observed in the corners of titanium-gold electrode devices and underneath indium-tin-oxide electrodes. Photodiodes with 3 μm wide fingers were found to have a depletion region which did not behave in a quasi-one-dimensional manner.