Performance of near-infrared InGaAs focal plane array with different series resistances to p-InP layer

Abstract

A planar-type InGaAs linear detector was designed and fabricated based on n-i-n⁺ type InP/In_0.53Ga_0.47As/InP epitaxial materials. The major process of the detector contains planar diffusion, surface passivation, metal contact and annealing. The I-V curves and the relative spectral response were measured at room temperature. The relative spectral response is in the range of 0.9 μm to 1.68 μm. The R₀A of the detector is about 2×10⁶ Ω•cm² and the dark current density is 5~10nA/cm² at -10mV bias voltage. The linear detectors were wire-bonded with readout integrated circuits (ROIC) to form focal plane array (FPA). The input stage of the ROIC is based on capacitive-feedback transimpedance amplifier (CTIA) with a capacitor (C_int) to be 0.1pF. However, the FPA signals are oscillating especially when close to the saturation. The ohmic contact on p-InP region plays an important role in the performance of detectors and FPAs. In this case, the series resistance to p-InP layer of each pixel is up to 1×10⁶Ω. The FPAs were simulated in case of InGaAs detectors with different series resistances. According to the simulation results, the bandwidth of CTIA is lowering along with Rs increasing, and the signals of the FPAs oscillate when the series resistances are beyond 4×10⁴Ω. The reason for the unstable oscillation of FPA is due to the series resistance of the detector which is too high enough. Then, the annealing process of the detectors was improved and the series resistances were lower than 1×10⁴Ω. The optimized InGaAs linear detectors were wire-bonded with the same ROIC. The oscillation of the signals disappears and the FPA shows good stability.