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

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 μm, 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 μm and a 0.25-μm absorption layer displayed a bandwidth of 19.5 GHz when biased at -15 V under front-side illumination with 1.55-μm light.