High-speed InGaAs metal-semiconductor-metal photodetectors with thin absorption layers

Abstract
The responsivity and the bandwidth of metal-semiconductor-metal photodetectors (MSMPD's) with different InGaAs absorption layer thicknesses and electrode geometries were investigated. By decreasing the InGaAs thickness from 1.0 to 0.25 /spl mu/m, the bandwidth was found to increase by approximately a factor of 2, while the responsivity was found to decrease by almost a factor of 3 from 0.29 to 0.10 A/W at a bias of -5 V. Devices with an electrode width and spacing of 1 /spl mu/m and a 0.25-/spl mu/m absorption layer displayed a bandwidth of 19.5 GHz when biased at -15 V under front-side illumination with 1.55-/spl mu/m light.