Valence band structure of polytypic zinc-blende/wurtzite GaAs nanowires probed by polarization-dependent photoluminescence

Abstract

We conducted temperature-dependent measurements of the photoluminescence (PL) polarization on GaAs nanowires (NWs) with polytypic zinc-blende/wurtzite structure in order to probe the symmetry and energy structure of the valence band in the wurtzite segments of the NWs. The low-temperature measurements revealed that in most of the investigated cases, the ground level of the interface excitons responsible for the PL is formed by the heavy hole. To describe the observed temperature dependence of the degree of PL polarization, we developed a theoretical model that allows an estimation of the splitting between the heavy hole and light hole exciton subbands in these NWs. This splitting is smaller than expected in pure wurtzite on the basis of recent first-principles calculations, which may be attributed to the multiple twinned nature of the wurtzite sections, which effectively behave as a polytype of lower hexagonality.

Charge carrier generation, relaxation, and recombination in polytypic GaAs nanowires studied by photoluminescence excitation spectroscopy

“…Since the C 7 c and C 8 c states show a light and heavy electron mass, respectively, 11,36 we propose that electronic confinement in WZ/ZB GaAs crystal-phase quantum discs leads to a heavy-electron light-electron mixing, in a way similar to the heavy-hole light-hole mixing reported in Ref. 39. The resulting conduction state would exhibit a high effective mass as well as a non-zero oscillator strength for recombination to the valence band, in agreement with experimental reports.…”

Polytypism in ZnS, ZnSe, and ZnTe: First-principles study

“…The influence of the optimized u on c/a and V , in general, is very small. However, its small deviation can significantly modify the local electronic properties and internal electric fields due to the spontaneous polarization in hexagonal polytypes [29][30][31][32][33]. This especially holds for heterocrystalline junctions and superlattices [34,35], or the presence of interfaces between two polytypes of one-and-thesame compound in the [0001] direction.…”

Optical study of the band structure of wurtzite GaP nanowires

“…[1][2][3][4][5] Semiconductor nanowires (NWs) have shown excellent control of the growth of ZB-WZ phases, [6][7][8][9] allowing crystal structure band engineering. [10][11][12] Recently, the Auseeded growth of high purity WZ GaP nanowires via vaporliquid-solid (VLS) method was demonstrated, and the optical properties have been investigated. [13][14][15][16][17][18] Photoluminescence (PL) measurements on patterned arrays of WZ GaP wires showed optical emission at 2.09 eV with a short lifetime of $0.8 ns, indicating a direct band gap semiconductor.…”