Polarized microphotoluminescence and reflectance spectroscopy of GaN with k perpendicular to c: Strongly pi-polarized line near the A exciton
2002 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, Vol. 65, no 7Article in journal (Refereed) Published
Polarized microphotoluminescence (mu-PL) and reflectivity studies of thick wurtzite GaN grown by hydride vapor phase epitaxy on c sapphire are performed with the light vector k both normal to the c axis (kperpendicular toc) and parallel to it. A strong PL peak is found in the vicinity of the A exciton in pi polarization (kperpendicular toc, E parallel to the c axis). in apparent contradiction to the selection rules. The pi-polarized component exceeds in intensity the sigma-polarized one up to similar to50 K. Power- and temperature-dependent measurements of both no-phonon and longitudinal optical phonon-assisted (monitoring the real density of exciton states) mu-PL reveal the complex nature of the pi-polarized PL line near the A exciton. At low temperatures the pi-component involves a bound B exciton contribution, while at higher temperatures contributions of scattered A exciton states become appreciable, The enhancement of the pi-polarized component is attributed to the complex structure of the exciton-polariton branches for kperpendicular toc. Temperature-dependent mu-PL and reflectance spectroscopies reveal additionally a difference in the optical properties between the sample regions at the top surface and the cleaved edges, tentatively explained as induced by different strains in these regions.
Place, publisher, year, edition, pages
2002. Vol. 65, no 7
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-47895DOI: 10.1103/PhysRevB.65.075212OAI: oai:DiVA.org:liu-47895DiVA: diva2:268791