  We demonstrate an Ensemble Monte Carlo (EMC) modeling approach for robust and
rigorous simulations of photovoltaic quantum cascade detectors (QCDs) in the
mid-infrared (mid-IR) and terahertz (THz) range. The existing EMC simulation
tool for quantum cascade lasers (QCLs) was extended to simulate the
photovoltaic transport effects in QCDs at thermal equilibrium under zero bias.
Here, we present the results of the EMC study of a THz detector design with a
detection wavelength of 84 $\mu$m. The simulation results show good agreement
with experimental data. For a temperature of 10 K we obtain a peak responsivity
of 9.4 mA/W.
