Comprehensive study of the electronic and optical behavior of highly degenerate p-type Mg-doped GaN and AlGaN

Journal Article · Wed Jan 28 04:00:00 EST 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4906464· OSTI ID:1211345

Gunning, BP; Fabien, CAM; Merola, JJ; Clinton, EA; Doolittle, WA; Wang, S; Fischer, AM; Ponce, FA

The bulk and 2-dimensional (2D) electrical transport properties of heavily Mg-doped p-type GaN films grown on AlN buffer layers by Metal Modulated Epitaxy are explored. Distinctions are made between three primary p-type conduction mechanisms: traditional valence band conduction, impurity band conduction, and 2D conduction within a 2D hole gas at a hetero-interface. The bulk and 2D contributions to the overall carrier transport are identified and the relative contributions are found to vary strongly with growth conditions. Films grown with III/V ratio less than 1.5 exhibit high hole concentrations exceeding 2 x 10(19) cm(-3) with effective acceptor activation energies of 51 meV. Films with III/V ratios greater than 1.5 exhibit lower overall hole concentrations and significant contributions from 2D transport at the hetero-interface. Films grown with III/V ratio of 1.2 and Mg concentrations exceeding 2 x 10(20) cm(-3) show no detectable inversion domains or Mg precipitation. Highly Mg-doped p-GaN and p-AlGaN with Al fractions up to 27% similarly exhibit hole concentrations exceeding 2 x 10(19) cm(-3). The p-GaN and p-Al0.11Ga0.89N films show broad ultraviolet (UV) photoluminescence peaks, which intercept the valence band, supporting the presence of a Mg acceptor band. Finally, a multi-quantum-well light-emitting diode (LED) and p-i-n diode are grown, both of which demonstrate rectifying behavior with turn-on voltages of 3-3.5V and series resistances of 6-10 Omega without the need for any post-metallization annealing. The LED exhibits violet-blue luminescence at 425 nm, while the p-i-n diode shows UV luminescence at 381 nm, and both devices still show substantial light emission even when submerged in liquid nitrogen at 77 K. (C) 2015 AIP Publishing LLC.

• Sponsoring Organization: USDOE Advanced Research Projects Agency - Energy (ARPA-E)
• DOE Contract Number: AR0000470
• OSTI ID: 1211345
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 4 Vol. 117; ISSN 0021-8979
• Country of Publication: United States
• Language: English