InGaAs metal-semiconductor-metal photodetectors with various barrier enhancement layers have been investigated. The responsivity at 1.55 mum wavelength varies between 0.21 and 0.43 A/W depending on layer structure, bias voltage and photosensitive area. Using a pseudomorphic In0.9Ga0.1P cap layer on InP for Schottky contacts, devices exhibit dark current densities as low as 44 muA/cm2. The responsivity is also much more linear than those of conventional devices with respect to both bias voltage and incident optical power level.
