Effects of electron doping level on minority carrier lifetimes in n-type mid-wave infrared InAs/lnAs_(1-x)Sb_x type-Ⅱ superlattices

摘要

The minority carrier lifetime (τ_(MC)) and equilibrium electron concentration (i.e., the doping level, n_0) are both important values that directly determine diffusion current in infrared photodetectors utilizing n-type absorbing regions. Here, time-resolved microwave reflectance measurements are used to non-destructively measure both of these values in mid-wave infrared InAs/InAs_(1-x)Sb_x type-Ⅱ superlattices with varying n-type doping levels between 2 × 10~(14) cm~(-3) and 2 × 10~(16) cm~(-3). The measured data are analyzed using carrier recombination theory to determine the doping level ranges where Shockley-Read-Hall (SRH), radiative, and Auger recombination limit τ_(MC). The optimal doping level, which minimizes dark current, is experimentally determined and corresponds to the electron density at which τ_(MC) switches from SRH limited to Auger limited behavior. A comparison of two InAs/InAs_(1-x)Sb_x photodetectors of different equilibrium electron densities demonstrates a decrease in dark current for a doping level near the optimal n_0τ_(MC) product.