High performance InGaAsP channel HFETs on InP for OEIC applications

InGaAs-based transistors have already been successfully integrated with PIN or MSM photodetectors to realize receivers for 1.3-1.55 μm optical transmissions. However, excess gate leakage current and low-frequency noise generally observed in lattice-matched InGaAs-channel FETs still severely limit receivers performances at moderate data rates (from hundreds of mbit/s up to a few gbit/s). InGaAsP quaternary alloy, which allows bandgap adjustment by varying phosphorous composition, constitutes an attractive solution to obtain low leakage, low noise FETs suitable for optoelectronic integration. In this paper, we present the fabrication and the characterization of InAlAs/InGaAsP HFETs. We first describe the device structure, reporting on its optimization through computer simulation and technological approach in order to enhance FET performances. Then, DC and RF characteristics of the device am presented. Low-frequency noise measurements are reported and discussed with photoreceiver performances in perspective. Experimental results on one to three-stage preamplifiers fabricated using these HFETs are finally presented and compared to similar GaAs or InP-based receivers