High responsivity, high speed InP-based inverted MSM photodetectors
The low capacitance per unit area of metal-semiconductor-metal (MSM) photodetectors detecting at 1.3 and 1.55 μm make them attractive for integration in OEIC receiver circuits. However, low responsivity is also an undesirable characteristic of MSMs. This article reports for the first time MSMs with high responsivities at 1.3 μm which have fingers on the bottom of the thin film devices, specifically an inverted MSM (I-MSM). The characteristics of the I-MSM are compared to conventional on-wafer MSMs (W-MSMs) and to MSMs reported in the literature with indium-tin-oxide transparent electrodes (ITO-MSMs).