SENSITIVITY COMPARISON OF MSM-HBT AND P-I-N-HBT OEIC RECEIVERS

The sensitivity of heterojunction-bipolar-transistor- (HBT-) based OEI C receivers with metal-semiconductor metal photodetectors (MSM-PD) or p-i-n photodetectors (p-i-n-PD) are compared. With an accurate small-s ignal circuit model of an InP/InGaAs HBT, it is shown that sensitivity of the p-i-n-HBT receiver is higher than char of the MSM-HBT receiver even though the high-frequency equivalent input noise current density is higher for the former than the latter. However; the HBT receiver u sing MSM-PD with light transparent conducting fingers would offer a po tential sensitivity improvement of 0.5 dB over the p-i-n-HBT receiver at la Gbit/s due to an increased responsivity of the MSM-PD. (C) 1995 John Wiley & Sons, Inc.