On the Ge shallow-to-deep level transition in Al-rich AlGaN.

Autor: Bagheri, Pegah, Reddy, Pramod, Mita, Seiji, Szymanski, Dennis, Kim, Ji Hyun, Guan, Yan, Khachariya, Dolar, Klump, Andrew, Pavlidis, Spyridon, Kirste, Ronny, Collazo, Ramón, Sitar, Zlatko
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Zdroj: Journal of Applied Physics; 8/7/2021, Vol. 130 Issue 5, p1-8, 8p
Abstrakt: Contrary to the arsenides where donors undergo stable DX transition, we find that Ge in AlGaN does not suffer from the DX transition; instead, it undergoes a shallow donor (30 meV) to deep donor (150 meV) transition at ∼50% Al content in the alloy. This finding is of profound technological importance as it removes fundamental doping limitations in AlGaN and AlN imposed by the presumed DX−1 acceptor state. The charge state of Ge below and above the transition was determined by co-doping with Si, which remains a shallow donor in AlGaN for up to 80% Al. It was found that Ge occupied a donor state with a (0/+) thermodynamic transition for AlGaN alloys below and above the transition. Ge as a shallow donor was completely ionized at room temperature; however, the ionization of the deep donor required elevated temperatures, commensurate with its higher ionization energy. This behavior is not unique to Ge; preliminary findings show that Si and O in AlGaN may behave similarly. [ABSTRACT FROM AUTHOR]
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