Design, fabrication, and performance of high-speed monolithically integrated InAlAs/InGaAs/InP MSM/HEMT photoreceivers

Abstract

A detailed study of the performance of monolithically integrated photoreceivers based on metal-semiconductor-metal (MSM) photodetectors (PD's) and HEMT's is undertaken. Two different stacked-layer approaches to integrating MSM-PD's with HEMT's are investigated, and the performance of detectors and HEMT's for each approach is compared. The structure with the MSM layers grown on top of the HEMT layers exhibited the best overall performance. A physics-based MSM model is developed and incorporated into microwave circuit design software; excellent agreement between circuit simulations and measured frequency responses is demonstrated. To evaluate the effects of MSM electrode geometry and detector area on photoreceiver performance, photoreceivers with MSM interelectrode spacings of 1, 1.5, and 2 μm were fabricated and characterized. The electrical amplifier used in the photoreceivers is a two-stage, variable-transimpedance amplifier with a common-gate HEMT as the feedback path. By adjusting the dc voltage applied to the gate of this feedback HEMT, transimpedances ranging from 55.8 to 38.1 dBΩ, with corresponding -3 dB cutoff frequencies from 6.3 to 18.5 GHz, were measured experimentally. Excellent noise performance has been measured, with average input noise current spectral densities of 7.5, 8, and 12 pA/Hz 1/2 obtained for bandwidths of 6.3, 8, and 13.7 GHz, respectively. A packaged receiver has been tested at 5 Gb/s and an open eye pattern obtained.