Binding energies of excitons in a strained wurtzite GaN/AlGaN quantum well influenced by screening and hydrostatic pressure

Abstract

In the framework of effective mass and single-band approximations, a variational method combined with a self-consistent procedure is adopted to discuss the binding energies of heavy-hole excitons in a strained wurtzite GaN/Al 0.3 Ga 0.7 N quantum well by considering the hydrostatic pressure effect and screening due to the electron-hole gas. The built-in electric field in such a structure produced by spontaneous polarization and strain-induced piezoelectric polarization is considered in our calculation. A simplified coherent potential approximation is extended to calculate the energy gaps of the ternary mixed crystal Al x Ga 1−x N. The result indicates that the binding energies of excitons increase nearly linearly with pressure even when taking into consideration the modification of strain. It is also found that the percentage increase of the binding energy with pressure is influenced by the electron-hole density due to the influence of pressure on the screening and exclusion effects. The excitonic binding energies increase obviously with decreasing barrier thickness due to the built-in electric field.

Screened excitons in strained wurtzite AlxGa1–xN/GaN/AlyGa1–yN quantum wells

“…For a given density, the variation of E b versus d w is qualitatively similar to that in conventional zinc-blende QWs [5][6][7]. It should be pointed out that the result in a previous paper [16] was undervalued due to processing the normalization of wavefunction Our results in symmetric structure case are in general agreement with the 2D values (seen Fig. 1 in reference [15]).…”

“…More recently, Pokatilov et al [15] studied theoretically the exciton states and photoluminescence spectra of strained wurtzite Al x Ga 1−x N/GaN QWs. Ha et al [16] discussed the screening effect from the 2-dimensional electron-hole gas (2DEHG) on the binding energies of excitons in wurtzite QWs with given sizes using a variational method combined with a self-consistent procedure.…”

Pressure Dependence of Exciton Binding Energy in GaN/AlxGa1 - xN Quantum Wells

“…This is probably caused by the fact that at high electric field, the effect of increased effective mass compensates the reduction of the Coulomb attraction between the electron and the hole. Our results, although in principle confirming the weak dependence of the exciton binding energy on pressure show opposite trends as compared to the simple model used in [4]. For lower concentration of Al in the barrier we predict a slight reduction of the binding energy with pressure while for higher contents, the binding energy is almost pressure insensitive or increases very slightly at very high electric field, while a simple single band model of excitons employed in [4] predicts increase of the exciton binding energy with pressure.…”

“…These studies based on the band to band photoluminescence measurements usually ignored the pressure effect on the exciton binding energy assuming that its contribution to the overall effect is small [2,3]. Recent theoretical analysis [4] employing a simple two band variational technique indicated that the exciton binding energy in GaN/Al x Ga 1−x N quantum wells with barrier composition x = 0.3 and well thickness equal to 30 Å indeed increases only slightly with pressure at the rate of about 0.1 meV per 1 GPa. In order to verify this result we applied a comprehensive model of excitonic spectra in wurtzite type quantum wells taking into account the complicated band structure in such systems.…”

Optical Absorption of Excitons in Strained Quasi 2D GaN Quantum Dot

“…The binding energies of heavy‐hole excitons in a strained wurtzite GaN/Al 0.3 Ga 0.7 N quantum well are reported by Ha et al, their results demonstrate that the excitonic binding energies increase considerably with increasing pressure. Recently, we have investigated the pressure effect on an exciton in a wurtzite AlN/GaN/AlN spherical core/shell quantum dot, our results reveal that the electron–hole distance becomes more attractive when the pressure is applied.…”