Effects of high-energy proton implantation on the luminescence properties of InAs submonolayer quantum dots

Herein, we demonstrate enhancement in photoluminescence (PL) efficiency of InAs submonolayer quantum dots (QDs) resulting from high-energy proton implantation. To obtain optimum energy of protons, we initially varied the energy from 2 MeV to 4.5 MeV at a fixed fluence of 2×1012 ions/cm2. At an optimum energy of 2.5 MeV, we varied the proton dose from 8×1011 to 1×1013 ions/cm2 to obtain the best PL response. As compared to the as-grown sample, all implanted samples exhibited PL enhancement, attributed to passivation of non-radiative recombination centers and annihilation of defects, with a consistent blue shift, attributed to out-diffusion of In atoms from the dots. From the PL results, a model was proposed for explaining the material improvement of implanted submonolayer QDs. All samples exhibited significant enhancement in thermal activation energies, confirming that proton implantation improved material quality. Finally, MESA-shaped single-pixel N-i-N detectors were fabricated for both as-grown and optimized samples (implanted with dose of 5×1012 ions/cm2 at an energy of 2.5 MeV) to measure the temperature-dependent dark current variation. At a temperature of 77 K and a bias of −0.20 V, the dark current density of ~4.5×10−4 A/cm2 of as-grown device was suppressed by more than one order to ~6×10−6 A/cm2 for the optimized sample.