Metal-semiconductor-metal photodetectors with InAlGaP capping and buffer layers

To improve the Schottky contact performance and carrier confinement of GaAs metal-semiconductor-metal photodetectors (MSM-PDs), we employed the wide bandgap material, In/sub 0.5/(Al/sub 0.66/Ga/sub 0.34/)/sub 0.5/P, for the capping and buffer layers. We directly evaluated the Schottky contact parameters on the MSM-PD structure. The reverse characteristics of the Schottky contacts were examined by taking into account the Schottky barrier height depended on the electric field in the depletion region, and hence on the applied bias. The ideality factor and Schottky barrier height of Ti-Pt-Au contacts to In/sub 0.5/(Al/sub 0.66/Ga/sub 0.34/)/sub 0.5/P are 1.02 and 1.05 eV, respectively. Extremely low dark currents of 70 and 620 pA were obtained for these MSM-PDs when they were operated at a reverse bias of -10 V at room temperature and at 70/spl deg/C, respectively.