Exciton localization behaviour in different well width undoped GaN/Al0.07Ga0.93N nanostructures
- 66 Downloads
We report results from optical spectroscopy such as photoluminescence (PL) and time resolved photo-luminescence (TRPL) techniques from different well width MOCVD grown GaN/Al0.07Ga0.93N MQW samples. There is evidence of localization at low temperature in all samples. The decay time of all samples becomes non-exponential when the detection energy is increased with respect to the peak of the emission. Localization of carriers (excitons) is demonstrated by the “S-shape” dependences of the PL peak energies on the temperature. The time-resolved PL spectra of the 3-nm well multi quantum wells reveal that the spectral peak position shifts toward lower energies as the decay time increases and becomes red-shifted at longer decay times. There is a gradient in the PL decay time across the emission peak profile, so that the PL process at low temperatures is a free electron-localized hole transition.
Keywordsphotoluminescence time-resolved photoluminescence quantum well exciton localization GaN/AlGaN
Unable to display preview. Download preview PDF.
- 5.A. Hangleiter, J.S. Im, H. Kollmer, S. Hepple, J. Off, and F. Scholz, “The role of piezoelectric fields in GaN — based quantum wells”, MRS Internet J. Nitride Semicond. Res. 3, 15 (1998).Google Scholar
- 8.M. Leroux, N. Grandjean, M. Laugt, J. Massies, B. Gil, P. Lefebvre, and P. Bigenwald, “Quantum confined stark effect due to built-in internal polarization fields in (Al, Ga)N/GaN quantum wells”, Phys. Rev. B58, R13371 (1998).Google Scholar
- 10.F. Bernardini, V. Fiorentini, and D. Vanderbilt, “Spontaneous polarization and piezoelectric constants of III–V nitrides”, Phys. Rev. B56, R10 024 (1997).Google Scholar
- 17.B. Monemar, H. Haratizadeh, P. Paskov, G. Pozina, P.O. Holtz, P. Bergman, S. Kamiyama, M. Iwaya, H. Amano, and I. Akasaki, “Influence of polarization fields and depletion fields on photoluminescence of AlGaN/GaN multiple quantum well structures”, Phys. Stat. Sol. (b) 237, 353 (2003).CrossRefADSGoogle Scholar
- 20.Y.P. Varshni, “Temperature dependence of the energy gap in semiconductors”, Physics 34, 149 (1967).Google Scholar