Optical deep level spectroscopy (ODLTS) and microcathodoluminescence (MCL) spectra were measured for a large group of n-GaN samples grown via metalorganic chemical vapor deposition (MOCVD), epitaxial lateral overgrowth (ELOG), or hydride vapor phase epitaxy (HVPE). In the MOCVD and ELOG samples, the ionization energy of dominant hole traps H1 was dependent on the excitation conditions and was ∼0.9 eV for high injection levels providing saturation of the ODLTS peak magnitude. The trap concentration increased with increasing Si donor concentration and correlated with the yellow band intensity in the MCL spectra. For the HVPE samples, the hole trap spectra were radically different from the MOCVD case: four hole traps-H2, H3, H4, and H5-with activation energies of 0.55, 0.65, 0.85, and 1.2 eV, respectively, were detected. In the MCL spectra, a broad green band that peaked near 2.5 eV was observed in addition to the usual yellow luminescence near 2.3 eV. This green band was attributed to the transitions involving the H4 hole traps. Possible identities of the hole traps detected in the MOCVD/ELOG and HVPE samples are discussed.
Bibliographical noteFunding Information:
The work at IRM was supported in part by International Science and Technology Center (ICTS) grant #3870. The work at Chonbuk University was supported by the National Research Foundation of Korea (NRF), funded by the Korean government (MEST) (2010-0019626, 2010-0026614). A.Y.P. gratefully acknowledges support from the Brain Pool Program of the Korean Government provided during his stay at Chonbuk National University. The work at UF is partially supported by HDTRA contract 11-1-0020 (Don Silversmith).
ASJC Scopus subject areas
- Physics and Astronomy(all)