Electric field and responsivity modeling for far-infrared blocked impurity band detectors

One-dimensional numerical modeling is presented for Ge:Ga far-infrared (IR) blocked impurity band (BIB) detectors in the low field, unity gain regime. Spatial variations of space charge, electric field, free carrier, and hopping currents are calculated to illustrate the effects of variations in absorbing layer compensation, blocking layer doping, and blocker/absorber interface gradient. Increased blocking layer doping and broader interface doping gradients lead to significant field variations. These field nonuniformities can increase responsivity by increasing field penetration and associated current collection in the absorbing layer. The ratio of photocurrent to dark current remains constant over a range of blocking layer doping, suggesting that extremely high purity blocking layers may not be required for far-IR BIB fabrication.