Internal emission metal-semiconductor-metal photodetectors on Si and GaAs for 1.3 μm detection

Si and GaAs metal-semiconductor-metal photodetectors with finger spacing as small as 0.25 μm are studied for 1.3 μm wavelength operation. It was found that the detectors have an external quantum efficiency as high as 0.5% for 1.3 μm light and a low dark current at room temperature. Increasing the Schottky barrier height reduces the responsivity of the detectors, but reduces the dark current more significantly and increases the responsivity-to-dark- current ratio. The condition for maximum signal-to-noise ratio was derived. Finally, the dependence of the detector's responsivity on the finger spacing was studied. Both the field-enhanced injection and charge-carrier screening were found to significantly affect the detector's responsivity.