Noise behaviour of InAlAs/GaInAs MSM photodetectors

Planar metal-semiconductor-metal (MSM) photodetectors are becoming increasingly popular for use in optoelectronic integrated circuits. A GaInAs absorption layer is used with a thin surface layer of a semiconductor and a higher Schottky barrier to limit the dark current for applications in the 1.3-1.6 mu m fibre bands. Planar photodetectors are prone to low-frequency noise because of traps at interfaces, and this may deteriorate the optical receiver performance. The authors investigate the noise in low-leakage AlInAs/GaInAs detectors and find that the excess low-frequency noise is limited to frequencies <1 MHz under normal operating conditions.