The effect of exciton localization on the optical and electrical properties of undoped and Si-doped Al_xGa_1−xN

Abstract

The properties of undoped and Si-doped Al x Ga 1−x N layers grown by metalorganic vapour-phase epitaxy have been investigated by photoluminescence and Hall effect measurements. The variable temperature photoluminescence properties of the layers were typical of Al x Ga 1−x N, with the temperature dependence of the peak energy showing the often-observed S-shape. The low and variable temperature photoluminescence properties of undoped material could be well described using alloy potential fluctuation theory. However, this was not the case for moderately Si-doped material, for which much larger S-shape behaviour, and thus larger exciton localization, was observed for samples with x > 0.3. The temperature dependence of the PL peak intensity of the Si-doped Al x Ga 1−x N layers, as well as their Hall activation energies, were then studied in order to obtain possible origins for the large increase in the exciton localization energy. It is tentatively proposed that the increase in the exciton localization could be related to the 9 → 7 valence band crossover, which occurs at roughly the same composition (0.2 < x < 0.3).

Impacts of Si-doping on vacancy complex formation and their influences on deep ultraviolet luminescence dynamics in AlxGa1−xN films and multiple quantum wells grown by metalorganic vapor phase epitaxy

“…To realize high electron concentration (n) by Si-doping, extensive studies have been carried out on Al x Ga 1−x N films with an emphasis on the growth conditions of MOVPE (Refs. [113][114][115][116], exciton localization, 117) changes in the roomtemperature PL spectra, 118,119) PAS results, 94,120) and estimation of h int NBE (Ref. 93).…”

“…The result implies that the heavily Si-doped sample contains highconcentration V III , because such DRCs have been ascribed to contain V III with different charge states. 43,48,55,[68][69][70][71][79][80][81][82][83][84][117][118][119] The T dependencies for the ratios of spectrally integrated CL intensities at given T (I CL T K ) to those at 12 K (I CL 12 K ) for the NBE emission, which are defined as a quenching ratio [ ( ) R T q ], of the samples displayed in Figs. 2(a ´-Si 1.9 10 cm ( ) R 300 K q were 11% and 0.015%, respectively.…”

The Effect of Exciton Localization on the Photoluminescence Properties of In0.01Al0.11Ga0.88N

“…In region I, it is assumed that the exciton is bound, in region II the exciton is progressing from a bound to a free state, and in region III excitons are considered as free (4). Therefore, the temperature dependence of the PL peak energy will be fitted according to the modified Varshni model for the temperature dependence of the band gap to define and discuss the localization energy, E loc , as the difference in energy between the fitted curve and the minimum of the measured peak energy in regions I and II (5,6).…”