Sensitivity of resonant tunneling diode photodetectors

We have studied the sensitivity of AlGaAs/GaAs double barrier resonant tunneling diode photodetectors with an integrated GaInNAs absorption layer for light sensing at the telecommunication wavelength of lambda = 1.3 mu m for illumination powers from pico- to microwatts. The sensitivity decreases nonlinearly with power. An illumination power increase of seven orders of magnitude leads to a reduction of the photocurrent sensitivity from S-I = 5.82 x 10(3) AW(-1) to 3.2 AW(-1). We attribute the nonlinear sensitivity-power dependence to an altered local electrostatic potential due to hole-accumulation that on the one hand tunes the tunneling current, but on the other hand affects the lifetime of photogenerated holes. In particular, the lifetime decreases exponentially with increasing hole population. The lifetime reduction results from an enhanced electrical field, a rise of the quasi-Fermi level, and an increased energy splitting within the triangular potential well. The non-constant sensitivity is a direct result of the non-constant lifetime. Based on these findings, we provide an expression that allows us to calculate the sensitivity as a function of illumination power and bias voltage, show a way to model the time-resolved photocurrent, and determine the critical power up to which the resonant tunneling diode photodetector sensitivity can be assumed constant.