A 40-Gb/s preamplifier using AlGaAs/InGaAs HBTs with regrown base contacts

A preamplifier for 40-Gb/s optical transmission systems incorporating AlGaAs/InGaAs heterojunction bipolar transistors (HBTs) with p/sup +/ regrown extrinsic base layers is described. The HBTs have a heavily doped regrown p/sup +/-GaAs layer in the extrinsic base regions and a thin graded InGaAs strained layer for the intrinsic base. Their measured peak f/sub max/ is above 200 GHz. The developed preamplifier provides a bandwidth of 38.4 GHz and a transimpedance gain of 41.1 dB /spl Omega/. Moreover, the frequency response as an optical receiver has a bandwidth of 32 GHz. These characteristics make the preamplifier suitable for use in a 40-Gb/s optical receiver. These results show that AlGaAs/InGaAs HBTs with p/sup +/ regrown extrinsic base layers are very promising for use in 40-Gb/s optical transmission systems.