Ground-state resonant two-photon transitions in wurtzite GaN/AlN quantum dots

Two-photon transition rates are investigated in resonance to the ground state transition in wurtzite GaN/AlN quantum dots using an 8-band kp-scheme. The ground state transition is two-photon accessible through the electron-hole separation inherent to wurtzite III-nitride heterostructures as a result of internal polarization fields. We show that this built-in parity breaking mechanism can allow deterministic triggering of single-photon emission via coherent two-photon excitation. Radiative lifetimes obtained for single-photon relaxation are in good agreement with available time-resolved micro-photoluminescence experiments, indicating the reliability of the employed computational framework. Two-photon singly-induced emission is explored in terms of possible non-degeneracy and cavity enhancement of two-photon processes.