Characteristics of a-GaN films and a-AlGaN/GaN heterojunctions prepared on r-sapphire by two-stage growth process

A. Y. Polyakov, Lee Woon Jang, N. B. Smirnov, A. V. Govorkov, E. A. Kozhukhova, T. G. Yugova, V. Y. Reznik, S. J. Pearton, Kwang Hyeon Baik, Sung Min Hwang, Sukkoo Jung, In Hwan Lee

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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 104cm -1. The residual donor concentration was 1014-10 15cm-3, with a very low density (2.5 10 13cm-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 E v 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 1013cm-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.

Original languageEnglish
Article number093709
JournalJournal of Applied Physics
Volume110
Issue number9
DOIs
Publication statusPublished - 2011 Nov 1

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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    Polyakov, A. Y., Jang, L. W., Smirnov, N. B., Govorkov, A. V., Kozhukhova, E. A., Yugova, T. G., Reznik, V. Y., Pearton, S. J., Baik, K. H., Hwang, S. M., Jung, S., & Lee, I. H. (2011). Characteristics of a-GaN films and a-AlGaN/GaN heterojunctions prepared on r-sapphire by two-stage growth process. Journal of Applied Physics, 110(9), [093709]. https://doi.org/10.1063/1.3658026