PL spectra for ternary alloy epitaxial layers with Al compositions of (a) 0.019, (b) 0.038, (c) 0.057, (d) 0.077, and (e) 0.092, measured at 5 K under an excitation power density of .
Variation in PL linewidth (closed circles) for ternary alloy epitaxial layers as a function of Al composition (, and 0.092). The open squares and open triangles represent the reported values of exciton linewidth from Coli et al. 6 and Steude et al.,5 respectively. The solid line indicates the theoretical calculation of the exciton linewidth reported by Coli et al. 6
Temperature evolution of PL spectra for an ternary alloy epitaxial layer. The excitation power density is estimated to be . The closed circles indicate the peaks of the PL spectra.
Temperature dependence of PL peak energy (closed circles) and PL linewidth (open circles) for an ternary alloy epitaxial layer. The solid and the dashed lines represent least-squares fits obtained from Eqs. (1) and (2), respectively.
Energy separation, , between the PL peak energy measured at 5 K and the energy predicted using the Varshni equation, as a function of Al composition. The dashed line indicates the least-squares fit. The inset shows the temperature dependence of the PL peak energy for an ternary alloy epitaxial layer at temperatures below 110 K. The solid line in the inset shows the fit obtained using the Varshni equation.
Thermal activation energies (a) and (b) , determined from a fit using Eq. (3), as a function of Al composition. Both the solid lines in (a) and (b) are given only to indicate the data trend. The inset shows an Arrhenius plot of PL intensity for an ternary alloy epitaxial layer. The dashed line in the inset indicates the fit obtained using Eq. (3).
Time integrated PL spectra for an alloy epitaxial layer at 7 K under an excitation energy density of . The closed circles indicate PL lifetimes as a function of emission energy. The dashed line indicates the fitting curve obtained using Eq. (4).
Dependence of (a) the tailing energy of localized states , (b) mobility edge , and (c) radiative lifetime at 7 K on the Al composition. The solid lines in (a) and (b) represent linear-least-squares fit. The solid line in (c) is given only to indicate the data trend.
Relationships of localization energy, , PL linewidth, and . The open circles represent the values reported by Nepal et al. 19 The solid line is a least-squares fit. The inset shows a linear plot for the relationship. The dashed and solid lines in the inset are least-squares fits using linear and power functions, respectively.
Summary of obtained parameters from fitting using Eqs. (1) and (2).
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