Improvement of Dark Current Using InP/InGaAsP Transition Layer in Large-Area InGaAs MSM Photodetectors

摘要

A large-area InGaAs metal-semiconductor-metal (MSM) photodetector with 1 × 1 mm{sup}2 photoactive area for free-space optical communication applications has been designed, fabricated, and characterized. Interdigitated electrodes of 2-μm widths and 15-μm spacings are designed to maximize the responsivity, and enable MSM photodetectors to reach a maximum responsivity at 1.53-μm wavelength. By employing a two-step InP/InGaAsP transition layer, the dark current density of 45 fA/μ m{sup}2 was achieved at 10-V bias and at room temperature. Dark current-bias voltage curves were measured as a function of temperature from 40 to 270 K to estimate the activation energy. A 3-dB bandwidth of 210 MHz was obtained at a 10-V bias, and the measured result was compared with the designed bandwidth.