Hybrid drift‐diffusion–TLM analysis of high‐speed and high‐output UTC traveling‐wave photodetectors

Abstract

AbstractThe scope of the hybrid drift‐diffusion (DD)–TLM method is extended to include the analysis of unitraveling‐carrier (UTC) photodetectors. The extended method takes into account the overshoot velocity at which electrons in the collector of an UTC photodiode drift. The method is used for large and small signal analysis of the UTC traveling‐wave photodetector (TWPD) and near‐ballistic (NB) UTC TWPD. It is shown that there is a trade‐off between the UTC TWPD's bandwidth and saturation current that has to be considered in the design. A higher bias voltage reduces the bandwidth, but also increases the saturation current of the photodetector. The presented UTC TWPD has bandwidths of 110 and 83 GHz and saturation currents of 15 and 30 mA under 1 and 5 V biases, respectively. To improve the performance under high bias voltage, the NB‐UTC TWPD is investigated. A maximum RF power of 6.5 dBm was obtained at 110 GHz under 5 V bias voltage. Copyright © 2007 John Wiley & Sons, Ltd.