Impulse response of metal-semiconductor-metal photodetectors using a conformal mapping technique and extracted circuit parameters

The impulse response of interdigitated InGaAs metal-semiconductor-metal photodetectors (MSMPDs) is modeled using a two dimensional transit-time calculation coupled with an equivalent circuit model of the intrinsic and parasitic elements of the MSMPDs. The simulated and experimental bandwidths of InGaAs MSMPDs with resistive transparent indium-tin-oxide and low-resistivity opaque titanium/gold electrodes are in excellent agreement and were found to be 6 and 11 GHz, respectively. The electrode width and spacing of these devices are 3μm and the active area is 2500 μm². This model aids in the design of MSMPDs with various electrode geometries, electrode materials, semiconductor materials, and methods of illumination.