Electrical properties, deep traps spectra and luminescence spectra were studied for two undoped a-plane GaN (a-GaN) films grown on r-plane sapphire using metalorganic chemical vapor deposition and differing by structural perfection. For sample A, the a-GaN film was directly deposited on AlN buffer. A two-step growth scheme was implemented for sample B, including an initial islanding growth stage and a subsequent enhanced lateral growth. Preliminary detailed X-ray analysis showed that the stacking faults density was 8 × 105 cm-1 for sample A and 1.7 × 105 cm-1 for sample B. Electrical properties of a-GaN films were largely determined by deep traps with a level near Ec -0.6 eV, with other prominent traps having the activation energy of 0.25 eV. The Fermi level was pinned by the Ec -0.6 eV deep traps for sample A, but shifted to the vicinity of the shallower 0.25 eV traps for sample B, most likely due to the reduced density of the 0.6 eV traps. This decrease of deep traps density is accompanied by a very pronounced improvement in the overall luminescence intensity. A correlation of the observed improvement in deep traps spectra and luminescence efficiency with the improved crystalline quality of the films is discussed.
|Number of pages||5|
|Journal||Materials Science and Engineering B: Solid-State Materials for Advanced Technology|
|Publication status||Published - 2010 Feb 15|
Bibliographical noteFunding Information:
The work at IRM was supported in part by RFBR grants # 07-02-13523-ofi-c , 08-02-00058-a . The work at Yale University was partly supported by the United States Department of Energy under contract DE-FC26-07NT43227 .
- Deep traps
- Extended defects
- Group III-nitrides
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering