Re-Examining the Doping Effect on the Performance of Quantum Well Infrared Photodetectors

This paper investigates the dependence of background limited performance (BLIP) temperature of quantum well infrared photodetectors (QWIPs) on doping density. In contrast to the generally accepted optimal doping condition E_F=k_BT_BLIP, our theoretical prediction shows that lower doping densities should slightly increase the BLIP temperature T_BLIP taking into account the temperature dependence of the Fermi energy E_F, a factor neglected in the previous analyses. Numerical modeling results are used to reinterpret the reported T_BLIP measurements for a series of QWIPs of typical design for 9 μm peak wavelength with different doping values. In addition, based on the same general expression for the Fermi energy, the optimized sheet doping concentration to achieve maximum detectivity is given by E_F=1.37 kBT, a revision to the previous E_F=2 k_BT condition.