Comprehensive study on molecular beam epitaxy-grown InAs sub-monolayer quantum dots with different capping combinations

Abstract

Here the authors report a comprehensive study on InAs sub-monolayer quantum dots with different capping layers. After performing systematic optimization of InAs deposition and GaAs thickness, they grew three samples, namely A, B and C, using solid-state molecular beam epitaxy with identical architecture but different capping materials (2 nm of GaAs, InGaAs-GaAs, and InAlGaAs-GaAs, respectively). Photoluminescence emission peaks due to the ground state transition from the dots were observed at 898, 917, and 867 nm for samples A, B, and C, respectively. Narrow full-width half-maxima (19–32 meV) of the emission peaks indicates high uniformity of dot size distribution. Using the conventional Arrhenius plot, the authors calculated the thermal activation energies from temperature-dependent photoluminescence experiment for samples A, B, and C as 49, 112, and 109 meV, respectively. To complete the study, single-pixel photodetectors were fabricated from samples A, B, and C and temperature-dependent dark current variation with applied bias voltage was measured. Dark current was calculated to be in the range of 10−5–10−4 A/cm2 at a 0.5 V applied bias at 77 K. The activation energies calculated from temperature-dependent dark current measurement for samples A, B, and C were 75, 160, and 155 meV, respectively, and followed the trend observed in temperature-dependent photoluminescence measurements.