The influence of phonons on the optical properties of GaN

Abstract

We comprehensively examine the importance of phonons on the optical properties of GaN. Using Raman and photoluminescence (PL) spectroscopies, the energies and linewidths of optic phonons, excitons, and discrete phonon sidebands (PSBs) are studied between 20 and 325 K. The temperature dependence of the A1 (LO) phonon energy and linewidth are described by a combined two- and three-phonon decay process. The narrow E22 phonon decays by the three-phonon emission process. Three band-edge excitons are observed in PL with linewidths between 2.8 and 5.3 meV at temperature 22 K. The energy gap shrinkage and exciton linewidths are completely interpreted based on electron-phonon interactions. The shift, broadening, and asymmetry of the PSBs are explained by incorporating the decay mechanism of A1 (LO) phonon and the exciton broadening from electron-phonon interactions.

Temperature dependence of the E2h phonon mode of wurtzite GaN/AlN quantum dots

“…24 Our analysis indicates that the two- phonon decay is the dominant mechanism involved in the increase in the E 2h phonon linewidth of the AlN spacer. On the other hand, similar as in bulk, 14 for the GaN QDs the evolution of the phonon width with temperature is better explained considering a symmetric three phonon decay channel. A comparison of the anharmonic A and B parameters of our sample with those of bulk 13,14 ͑see Table I͒ indicates an increase in their values by a factor of 2.7 for the GaN QDs and only 1.4 for the AlN spacer.…”

“…On the other hand, similar as in bulk, 14 for the GaN QDs the evolution of the phonon width with temperature is better explained considering a symmetric three phonon decay channel. A comparison of the anharmonic A and B parameters of our sample with those of bulk 13,14 ͑see Table I͒ indicates an increase in their values by a factor of 2.7 for the GaN QDs and only 1.4 for the AlN spacer. This difference could be due to the larger confinement effects expected in QDs than in the two-dimensional spacer.…”

“…13 In bulk GaN, due to the large frequency gap between the E 2h mode and the acoustic branches, three-phonon decay channels dominate. 14 Besides depending on the details of phonon dispersion, the interaction among optical phonons may be influenced by the presence of interfaces and confinement effects. In this respect, investigations performed on Si nanocrystals of various sizes indicated an increase in the value of the phonon decay anharmonic parameters as the crystal size was decreased.…”

Development of junction temperature estimation system for light-emitting LED using pulsed-laser Raman scattering

“…The vertical axis represents the signal intensity accumulated for 20,000 laser shots by the photon counting mode of the gated-ICCD. The horizontal axis represents the relative shift of the GaN-E 2 H Raman peak from the one at 0 K, in which the peak shift at the room temperature (20°C) is obtained of 66.5 nm by Song et al [11]. As can be seen in Fig.…”

Debye-Waller Factor in an Isotopically Disordered Semiconductor Crystal

“…It is determined in compound semiconductors by utilizing a recently proposed eight-parameter bond-bending force model [16] and in ternary chalcopyrite semiconductors from the available bulk modulus, and interionic separation distances [17]. The progress of research in semiconductor physics is achieved due to its (DWF) use to find the magnetic form factor of Eu 2+ in EuS [18], local structural properties in the terahertz semiconductor Zn 1−x Cd x Te [19], to describe observed band gap dependence [20], thermodynamic properties of semiconductor compounds [21], and vibrational dynamics and band structure of methylterminated Ge(111) [22]. The temperature dependence of DWF is governed by the molecular dynamics study * e-mail: dgsureshc@yahoo.co.in; scgairola@rediffmail.com in InSb [23], calculated from ab initio force constants in sphalerite III-V semiconductors [24], and also obtained from statistical moment method in compound semiconductors [25].…”