Coexistence of Shallow and Localized Donor Centers in Bulk GaN Crystals Studied by High-Pressure Raman Spectroscopy

Perlin, P.; Suski, T.; Polian, A.; Chervin, J. C.; Knap, W.; Camassel, Jean; Grzegory, I.; Porowski, S.; Erickson, Jon W.

doi:10.1557/proc-449-689

Cited by 5 publications

(5 citation statements)

References 14 publications

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“…The high-pressure experiments have also shown that freezeout of carriers occurs at pressures exceeding 20 GPa. 131,[133][134][135] Originally this observation was interpreted as consistent with the presence of nitrogen vacancies, since the V N donor gives rise to a resonance in the conduction band, which emerges into the band gap under pressure. However, the observations are also entirely consistent with a ''DX-like'' behavior of the oxygen donor.…”

Section: Oxygenmentioning

confidence: 92%

See 1 more Smart Citation

First-principles calculations for defects and impurities: Applications to III-nitrides

Walle

Neugebauer

2004

Journal of Applied Physics

2,821

2,197

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First-principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we describe the state-of-the-art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors. We will pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels. In the second part of the review we will illustrate these capabilities with examples for defects and impurities in nitride semiconductors. Point defects have traditionally been considered to play a major role in wide-band-gap semiconductors, and first-principles calculations have been particularly helpful in elucidating the issues. Specifically, calculations have shown that the unintentional n-type conductivity that has often been observed in as-grown GaN cannot be attributed to nitrogen vacancies, but is due to unintentional incorporation of donor impurities. Native point defects may play a role in compensation and in phenomena such as the yellow luminescence, which can be attributed to gallium vacancies. In the section on impurities, specific attention will be focused on dopants. Oxygen, which is commonly present as a contaminant, is a shallow donor in GaN but becomes a deep level in AlGaN due to a DX transition. Magnesium is almost universally used as the p-type dopant, but hole concentrations are still limited. Reasons for this behavior are discussed, and alternative acceptors are examined. Hydrogen plays an important role in p-type GaN, and the mechanisms that underlie its behavior are explained. Incorporating hydrogen along with acceptors is an example of codoping; a critical discussion of codoping is presented. Most of the information available to date for defects and impurities in nitrides has been generated for GaN, but we will also discuss AlN and InN where appropriate. We conclude by summarizing the main points and looking towards the future.

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Section: Oxygenmentioning

confidence: 92%

“…131 It has been established that the characteristics of these samples ͑obtained from high-pressure studies͒ are very similar to epitaxial films which are intentionally doped with oxygen. 132,133 The n-type conductivity of bulk GaN can therefore be attributed to unintentional oxygen incorporation.…”

Section: Oxygenmentioning

confidence: 99%

First-principles calculations for defects and impurities: Applications to III-nitrides

Walle

Neugebauer

2004

Journal of Applied Physics

2,821

2,197

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“…The n-type conductivity of bulk GaN can therefore be attributed to unintentional oxygen incorporation. The high-pressure experiments have also shown that freezeout of carriers occurs at pressures exceeding 20 GPa [12,14,15]. Originally this observation was interpreted as consistent with the presence of nitrogen vacancies, since the V N donor gives rise to a resonance in the conduction band, which emerges into the band gap under pressure.…”

Section: N-type Dopingmentioning

confidence: 91%

“…High levels of n-type conductivity have always been found in GaN bulk crystals grown at high temperature and high pressure [12]. Recent high-pressure studies have established that the characteristics of these samples are very similar to epitaxial films which are intentionally doped with oxygen [13,14]. The n-type conductivity of bulk GaN can therefore be attributed to unintentional oxygen incorporation.…”

Section: N-type Dopingmentioning

confidence: 99%

Theory of doping and defects in III–V nitrides

Walle

Stampfl

Neugebauer

1998

Journal of Crystal Growth

206

129

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“…High levels of n-type conductivity have traditionally been found in GaN bulk crystals grown at high temperature and high pressure [18]. High-pressure studies have recently established that the characteristics of these samples are very similar to epitaxial films that are intentionally doped with oxygen [19,20].…”

Section: Nitrogen Vacancies Versus Unintentional Impuritiesmentioning

confidence: 99%

Defects and Defect Reactions in Semiconductor Nitrides

et al. 1999

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We report a comprehensive investigation of native point defects and impurities in GaN, MN, and AlGaN alloys, with the goal of understanding doping limitations in nitride semiconductors. Unintentional incorporation of impurities (mainly oxygen) explains the tendency of nitride semiconductors to exhibit n-type conductivity. Silicon is the n-type dopant of choice; it remains shallow in AlGaN up to high Al content, while oxygen undergoes a DX transition. Experimental evidence for DX centers will be discussed. In p-type material, Mg doping is hindered by an increase in ionization energy with increasing Al content in AlGaN, and by nitrogen vacancies acting as compensating centers. Complex formation between magnesium and oxygen and between magnesium and nitrogen vacancies will be discussed.

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Coexistence of Shallow and Localized Donor Centers in Bulk GaN Crystals Studied by High-Pressure Raman Spectroscopy

Cited by 5 publications

References 14 publications

First-principles calculations for defects and impurities: Applications to III-nitrides

First-principles calculations for defects and impurities: Applications to III-nitrides

Theory of doping and defects in III–V nitrides

Defects and Defect Reactions in Semiconductor Nitrides

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