The nature of the DX state in Ge-doped AlGaN
Abstract
Electrical conductivity in high Al-content AlGaN has been severely limited, presumably due to a DX transition forming an acceptor state and subsequent self-compensation, which imposed an upper limit on the achievable free carrier concentration. To elucidate this idea, this paper examines Ge doping as a function of Al-content in AlGaN and finds a different behavior: for Al compositions below 40%, Ge behaved as a shallow donor with an ionization energy below 20 meV, while for Al compositions above 40%, above DX transition, it emerged as a deep donor. The ionization energy of this deep state increased with increasing Al content and reached 150 meV for 60% AlGaN. Around the DX transition, a continuous change from the shallow to deep donor was observed. In contrast to the density functional theory predictions, acceptor-type states corresponding to a DX-type transition were not observed. This finding may have profound technological consequences for the development of AlGaN- and AlN-based devices as it offers a feasible pathway to high n-conductivity in these compounds.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 01, 2020
- Source ID
- 10.1063/5.0008362
Entities
People
- Biplab Sarkar
- Pegah Bagheri
- Pramod Reddy
- Ramón Collazo
- Ronny Kirste
- Seiji Mita
- Shun Washiyama
- Zlatko Sitar
Organizations
- Air Force Office of Scientific Research
- Army Research Office
- National Science Foundation
- North Carolina State University
- United States Department of Energy