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Characteristics of a-GaN films and a-AlGaN/GaN heterojunctions prepared on r-sapphire by two-stage growth process.
- Source :
- Journal of Applied Physics; Nov2011, Vol. 110 Issue 9, p093709, 6p, 2 Black and White Photographs, 7 Graphs
- Publication Year :
- 2011
-
Abstract
- The electrical properties, presence of deep electron and hole traps and photoluminescence spectra were measured for undoped a-GaN films grown by metal-organic chemical vapor deposition (MOCVD) in a two-stage process using a high V/III ratio at the first stage and low V/III ratio at the second stage. Growth was performed on r-sapphire substrates with a high temperature GaN nucleation layer. The films showed a full width at half maximum of 450-470 arcseconds for the (11-20) x-ray rocking curve with little anisotropy with respect to the sample rotation around the growth direction. The stacking fault (SF) density determined by selective etching was ∼5 × 104 cm-1. The residual donor concentration was 1014-1015 cm-3, with a very low density (2.5 × 1013 cm-3) of electron traps located at Ec - 0.6 eV, which are believed to be one of the major non-radiative recombination centers in nonpolar GaN. Consequently, the films showed a high intensity of bandedge luminescence with negligible contribution from defect bands associated with SFs. In contrast to previously studied nonpolar GaN films, the a-GaN layers showed a high concentration of gallium-vacancy-related acceptors near Ev + 1 eV and a strong yellow luminescence band, both indicating that growth conditions were effectively N-rich. a-AlGaN/GaN heterojunctions with thin heavily Si doped AlGaN barriers made on a-GaN substrates showed two-dimensional electron gas (2DEG) concentrations of 1.2 × 1013 cm-3, with 2DEG mobility of 80 cm2/Vs. Capacitance-voltage profiling of Schottky diodes on these HJs suggest that the 2DEG is fully depleted by the built-in voltage of the Schottky diode. [ABSTRACT FROM AUTHOR]
- Subjects :
- GALLIUM nitride
PHOTOLUMINESCENCE
ALUMINUM compounds
HETEROJUNCTIONS
SAPPHIRES
Subjects
Details
- Language :
- English
- ISSN :
- 00218979
- Volume :
- 110
- Issue :
- 9
- Database :
- Complementary Index
- Journal :
- Journal of Applied Physics
- Publication Type :
- Academic Journal
- Accession number :
- 67225670
- Full Text :
- https://doi.org/10.1063/1.3658026