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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 x 10(12) ions/cm(2). At an optimum energy of 2.5 MeV, we varied the proton dose from 8 x 10(11) to 1 x 10(13) ions/cm(2) 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 x 10(12) ions/cm(2) 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 similar to 4.5 x 10(-4) A/cm(2) of as-grown device was suppressed by more than one order to 6 x 10(-6) A/cm(2) for the optimized sample. (C) 2015 Elsevier B.V. All rights reserved.

Graphical abstract: - Abstract: Here we propose a carrier transport mechanism for low energy H{sup −} ions implanted InAs/GaAs quantum dot infrared photodetectors supportive of the experimental results obtained. Dark current density suppression of up to four orders was observed in the implanted quantum dot infrared photodetectors, which further demonstrates that they are effectively operational. We concentrated on determining how defect-related material and structural changes attributed to implantation helped in dark current density reduction for InAs/GaAs quantum dot infrared photodetectors. This is the first study to report the electrical carrier transport mechanism of H{sup −} ion-implanted InAs/GaAs quantum dot infrared photodetectors.

The development of unsteady mixed convection flow of an incompressible laminar viscous fluid over a vertical cone has been investigated when the fluid in the external stream is set into motion impulsively, and at the same time the surface temperature is suddenly changed from its ambient temperature. The problem is formulated in such a way that at t = 0, it reduces to Rayleigh type of equation and as t ? ?, it tends to Falkner-Skan type of equation. The scale of time has been selected such that the traditional infinite region of integration become finite which significantly reduce the computational time. The coupled non-linear partial differential equations governing the unsteady mixed convection flow have been solved numerically by using an implicit finite-difference scheme in combination with the quasi-linearization technique. There is a smooth transition from the initial steady state to the final steady state. The velocity, temperature, and concentration profiles and their gradients at the surface for various values of the governing parameters are reported in the present study. � 2006 Elsevier Ltd. All rights reserved.