Importance of excitonic effects and the question of internal electric fields in stacking faults and crystal phase quantum discs: The model-case of GaN

Abstract

Laser field and electric field effects on exciton states and optical properties in zinc-blende GaN/AlGaN quantum wellWe compute using envelope function calculations the energy and the oscillator strength of excitons in zinc-blende/wurtzite quantum wells (QWs), such as those that appear in many examples of semiconductor nanowires, and in basal plane stacking faults (BSFs). We address specifically the model-case of GaN. In addition to the electron-hole Coulomb interaction, we account for the quantum-confined Stark effect. We demonstrate that despite the type-II band alignment at the zincblende/wurtzite interfaces, a significant binding and a rather strong oscillator strength are preserved by excitonic effects. When adjacent crystal phase QWs are coupled together, we compute increased as well as decreased exciton oscillator strength with respect to the single QW case, depending on the QW-QW coupling scheme. Comparing the results of our calculations with available data, we finally conclude in favor of the absence of built-in electric fields perpendicular to the BSF planes. V C 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4749789] 053512-2 P. Corfdir and P. Lefebvre J. Appl. Phys. 112, 053512 (2012) [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 131.230.73.202 On: Sun, 21 Dec 2014 02:08:53 053512-3 P. Corfdir and P. Lefebvre J. Appl. Phys. 112, 053512 (2012) [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 131.230.73.202 On: Sun, 21 Dec 2014 02:08:53 053512-5 P. Corfdir and P. Lefebvre

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

“…17 In particular, where the local fault density is high, coupling between successive crystal-phase quantum discs leads to a decrease of the exciton energy of the quantum disc. 31 In agreement with the transmission electron microscopy measurements performed on similar nanowires, 17 the micro-PL scan in Figure 2(a) confirms the model that the two tips of our wires show ZB and WZ crystal structures with low twinning and stacking fault densities, respectively, and the central segments of the wires exhibit repeated alternation between WZ and ZB crystal structures.…”

Temperature-Dependence of Exciton Radiative Recombination in (Al,Ga)N/GaN Quantum Wells Grown on a-Plane GaN Substrates

“…To compute E loc , we use envelope function calculations that include a variational modeling of excitonic effects. 18) We assume that exciton localization occurs on monolayer fluctuation of the QW thickness 19) and we get E loc ¼ 8, 3, and 1 meV for the 2-, 4-, and 7-nm-thick QWs. The computed QW width dependence of E loc agrees qualitatively with the localization energies deduced from the temperature-dependent PL experiments reported in Ref.…”

Effect of stacking faults on the photoluminescence spectrum of zincblende GaN

“…In this model, a type II band alignment is assumed, with band offsets of 270 meV and 70 meV for the conduction and valence bands 35 . The spontaneous polarisation of the wz-GaN differs from the zb-GaN, as detailed in Table I: the change in polarisation at the SF interface therefore results in electric fields in both the zb-and wz-GaN as illustrated in Fig.…”