^{1,a)}, Yoichi Yamada

^{1}, Tsunemasa Taguchi

^{1}, Akihiko Ishibashi

^{2}, Yasutoshi Kawaguchi

^{2}and Toshiya Yokogawa

^{2}

### Abstract

The optical properties of Ga-rich (, and 0.092) ternary alloy epitaxial layers have been studied by means of temperature-dependent photoluminescence(PL) and time-resolved PL spectroscopy. The luminescence intensity of excitons in five epitaxial layers indicated a thermal quenching process with two activation energies. The two quenching activation energies were attributed to the delocalization of excitons and thermal dissociation of excitons. Anomalous temperature dependence of the PL peak energy was also observed in the epitaxial layers, which enabled the evaluation of the localization energy of the excitons. The localization energy increased as the 1.7th power of the PLlinewidth, which reflected a broadening of the density of localized exciton states. In addition, the luminescence decay of the localized excitons for the five epitaxial layers became longer with decreasing emission energy. These observations suggest that the decay of excitons is caused not only by radiative recombination, but also by transfer to lower energy states.

This work was partly supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.

I. INTRODUCTION

II. EXPERIMENTAL

III. EXPERIMENTAL RESULTS

A. Localized excitonluminescence

B. Temperature dependence of excitonluminescence

C. TR luminescence

IV. DISCUSSION

V. CONCLUSION

## Figures

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 .

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}

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 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.

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.

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).

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).

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.

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.

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.

## Tables

Summary of obtained parameters from fitting using Eqs. (1) and (2).

Summary of obtained parameters from fitting using Eqs. (1) and (2).

Article metrics loading...

Full text loading...

Commenting has been disabled for this content