Photocurrent modeling and detectivity optimization in a resonant-tunneling quantum-dot infrared photodetector

Theoretical modeling of the photocurrent and detectivity optimization of a resonant-tunneling quantum-dot infrared photodetector (RT-QDIP) based on nonequilibrium Green's function (NEGF) is presented. The interaction with light used in the model is based on the first-order dipole approximation and the Fermi golden rule, which is used to obtain the transition rates due to photon emission or absorption. The bound states of the QD are obtained by solving numerically the eigenvalue problem of the Hamiltonian of the QD, while the continuum states are obtained from the retarded Green's function. The in-scattering and out-scattering self-energy functions due to photon interactions are calculated from the total transition rate and the quasi-Fermi level of the QD. The Green's functions of the QDs are obtained by numerically solving their governing kinetic equations using the method of finite differences. A quantum transport equation using the Green's functions is formed to calculate the dark and photocurrent. The model has been applied to simulate the dark current and responsivity of the RT-QDIP at different temperatures and applied biases. The simulated dark current and responsivity with this model are in good agreement with experimental results. The model was used to study the effect on the dark current and the responsivity resulting from changing the QD doping density and the barrier separation between QD layers. The detectivity is obtained for different design parameters. The model used is general and can be used as a tool for the design and prediction of the dark and photocurrent characteristics of different QDIP.