Effects of Sb/As intermixing on optical properties of GaSb type-II quantum dots in GaAs grown by droplet epitaxy

Abstract

Optical properties of GaSb type-II quantum dots (QDs) in GaAs were studied and compared with a theoretical model to clarify how the spatial overlap of holes in the dot and electrons outside is affected by the interdiffusion of Sb and As. GaSb QDs were grown in a GaAs substrate by droplet epitaxy and annealed at the temperature Ta=650–850 °C to induce the Sb/As intermixing. Photoluminescence (PL) studies showed that the integrated PL intensity I decreases to less than 1/10 as Ta is raised from 650 to 750 °C, while I increases by three orders of magnitude with the increase of Ta from 750 to 850 °C. This behavior is explained by the overlap Θ between electron and hole wave functions; in an initial stage of the interdiffusion, the mixing occurs only near the dot/matrix boundary, leading to the decrease in the overlap Θ, since electrons are more repelled by the dot. In later stages, however, the hole confinement and the electron repulsion in the dot both weaken, leading to the increase in the overlap Θ.

The influence of background As on GaSb/GaAs quantum dots and its application in infrared photodetectors

“…The phenomenon suggests that with decreasing Sb/background As ratios, the severe As-for-Sb exchange would result in a less abrupt GaSb/ GaAs interfaces. In this case, more electron-hole wave function overlapping would be obtained for the type-II nanostructures such that the optical recombination prob- ability would increase [9]. To further explain this phenomenon, a simply scheme is shown in the Fig.…”

Effects of Ga deposition rate and Sb flux on morphology of GaSb quantum dots formed on GaAs

“…In GaSb/GaAs hetero-junctions, the band lineup exhibits a type-II structure, wherein electrons and holes are spatially separated at the heterointerface [1]. This unique electronic configuration leads to optical properties quite different from those of type-I systems, such as a long radiative lifetime, confinement-potential-dependent oscillator strength, and large tunability of emitted photons [1][2][3][4]. The fabrication of quantum dots (QDs) of such antimonybased semiconductors will facilitate application in advanced photonic devices, and the understanding of the growth process is essential to controlling QD formation.…”

Excitation power dependence of photoluminescence spectra of GaSb type-II quantum dots in GaAs grown by droplet epitaxy

“…A GaSb QD in GaAs is one of such systems, where only holes are confined in the dot, and electrons remain around the dot. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] In earlier studies, GaSb/GaAs QDs have been formed mainly in Stranski-Krastanov (SK) mode, since 10-nm scale QDs are spontaneously grown just by depositing source materials on a lattice mismatched substrate. [10][11][12][13][14][15][16][17][18][19][20][21][22]25,27 In the process of QD formation by SK growth, a thin wetting layer (WL) is automatically fabricated and may affect their optical properties.…”

“…One can also grow GaSb/GaAs QDs by droplet epitaxy; Ga droplets are first formed and then exposed to Sb molecules. 23,24,26,28 This second approach has several advantages, including high controllability of QD density and shape, a wider choice of constituent materials, and an abrupt boundary between each QD and the matrix. In addition, WL thickness can be tuned.…”