Optimal Doping Density for Quantum-Well Infrared Photodetector Performance

We present a systematic study on a set of n-type GaAs-AlGaAs quantum-well infrared photodetectors (QWIPs) with varying Si doping density in the wells. It is revealed that the increase in doping density enhances proportionally the absorption-efficiency and responsivity while increasing exponentially the dark current and hence the dark current noise. We experimentally confirm the theoretically predicted optimum conditions for background-limited infrared performance temperature and detector-noise-limited detectivity. It is suggested that, to achieve the optimal QWIP performance, the doping density in the wells should be determined according to application and the desired operating temperature. We point out that a simulation is highly recommended to achieve the best possible performance since the choice of doping may not be obvious. As shown here, an optimized doping for temperature is actually the worst for detectivity for the particular set of samples.