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.
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1 June 2020
Research Article|
June 03 2020
The nature of the DX state in Ge-doped AlGaN
Pegah Bagheri
;
Pegah Bagheri
a)
1
Department of Materials Science and Engineering, North Carolina State University
, Raleigh, North Carolina 27695, USA
a)Author to whom correspondence should be addressed: [email protected]
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Ronny Kirste;
Ronny Kirste
2
Adroit Materials
, Cary, North Carolina 27518, USA
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Pramod Reddy
;
Pramod Reddy
2
Adroit Materials
, Cary, North Carolina 27518, USA
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Shun Washiyama
;
Shun Washiyama
1
Department of Materials Science and Engineering, North Carolina State University
, Raleigh, North Carolina 27695, USA
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Seiji Mita;
Seiji Mita
2
Adroit Materials
, Cary, North Carolina 27518, USA
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Biplab Sarkar
;
Biplab Sarkar
1
Department of Materials Science and Engineering, North Carolina State University
, Raleigh, North Carolina 27695, USA
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Ramón Collazo;
Ramón Collazo
1
Department of Materials Science and Engineering, North Carolina State University
, Raleigh, North Carolina 27695, USA
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Zlatko Sitar
Zlatko Sitar
1
Department of Materials Science and Engineering, North Carolina State University
, Raleigh, North Carolina 27695, USA
2
Adroit Materials
, Cary, North Carolina 27518, USA
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a)Author to whom correspondence should be addressed: [email protected]
Appl. Phys. Lett. 116, 222102 (2020)
Article history
Received:
March 21 2020
Accepted:
May 26 2020
Citation
Pegah Bagheri, Ronny Kirste, Pramod Reddy, Shun Washiyama, Seiji Mita, Biplab Sarkar, Ramón Collazo, Zlatko Sitar; The nature of the DX state in Ge-doped AlGaN. Appl. Phys. Lett. 1 June 2020; 116 (22): 222102. https://doi.org/10.1063/5.0008362
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