We have fabricated mid-wave infrared photodetectors containing InAsSb absorber regions and AlAsSb barriers in
n-barrier-n (nBn) and n-barrier-p (nBp) configurations, and characterized them by current-voltage, photocurrent, and
capacitance-voltage measurements in the 100-200 K temperature range. Efficient collection of photocurrent in the nBn
structure requires application of a small reverse bias resulting in a minimum dark current, while the nBp devices have
high responsivity at zero bias. When biasing both types of devices for equal dark currents, the nBn structure exhibits a
differential resistance significantly higher than the nBp, although the nBp device may be biased for arbitrarily low dark
current at the expense of much lower dynamic resistance. Capacitance-voltage measurements allow determination of the
electron concentration in the unintentionally-doped absorber material, and demonstrate the existence of an electron
accumulation layer at the absorber/barrier interface in the nBn device. Numerical simulations of idealized nBn devices
demonstrate that photocurrent collection is possible under conditions of minimal absorber region depletion, thereby
strongly suppressing depletion region Shockley-Read-Hall generation.
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