Electronic properties of the residual donor in unintentionally doped β-Ga2O3
Electron paramagnetic resonance was used to study the donor that is responsible for the n-type conductivity in unintentionally doped (UID) β-Ga2O3 substrates. We show that in as-grown materials, the donor requires high temperature annealing to be activated. In partly activated materials with the don...
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Veröffentlicht in: | Journal of applied physics 2016-12, Vol.120 (23) |
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Hauptverfasser: | , , , , , , , , , , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Electron paramagnetic
resonance was used to study the donor that is responsible
for the n-type conductivity in unintentionally doped (UID)
β-Ga2O3 substrates. We show that in as-grown
materials, the donor requires high temperature annealing to be activated. In
partly activated materials with the donor concentration in the
1016 cm−3 range or lower, the donor is found to behave
as a negative-U center (often called a DX center) with the negative charge state
DX− lying ∼16–20 meV below the neutral charge state d0
(or Ed), which is estimated to be ∼28–29 meV below the conduction
band minimum. This corresponds to a donor activation energy
of Ea∼44–49 meV. In fully activated materials with the donor spin
density close to ∼1 × 1018 cm−3, donor electrons become
delocalized, leading to the formation of impurity bands, which reduces the donor
activation
energy to Ea∼15–17 meV. The results clarify the
electronic structure of the dominant donor in UID β-Ga2O3
and explain the large variation in the previously reported donor activation
energy. |
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ISSN: | 0021-8979 1089-7550 1089-7550 |
DOI: | 10.1063/1.4972040 |