Stability, diffusion, and complex formation of beryllium in wurtzite GaN

Limpijumnong, Sukit; Walle, Chris G. Van de; Neugebauer, Jörg

doi:10.1557/proc-639-g4.3

Cited by 3 publications

(9 citation statements)

References 9 publications

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“…One problem for Be, however, is that the atom is too small and can incorporate efficiently on the interstitial site, where it acts as a double donor. 30,[40][41][42] Therefore, among the group-II impurities, Mg and Be are the most promising p-type dopants for GaN, and Be appears to be the best candidate, provided that the conditions that suppress formation of Be i donors can be established. This is technologically challenging to say the least.…”

Section: Substitutional Acceptorsmentioning

confidence: 99%

Luminescence properties of defects in GaN

Reshchikov¹,

Morkoç̌²

2005

Journal of Applied Physics

1,828

119

1,666

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Gallium nitride ͑GaN͒ and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet ͑UV͒ emitters and detectors ͑in photon ranges inaccessible by other semiconductors͒ and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these nitride semiconductors. Even though GaN broke the long-standing paradigm that high density of dislocations precludes acceptable device performance, point defects have taken the center stage as they exacerbate efforts to increase the efficiency of emitters, increase laser operation lifetime, and lead to anomalies in electronic devices. The point defects include native isolated defects ͑vacancies, interstitial, and antisites͒, intentional or unintentional impurities, as well as complexes involving different combinations of the isolated defects. Further improvements in device performance and longevity hinge on an in-depth understanding of point defects and their reduction. In this review a comprehensive and critical analysis of point defects in GaN, particularly their manifestation in luminescence, is presented. In addition to a comprehensive analysis of native point defects, the signatures of intentionally and unintentionally introduced impurities are addressed. The review discusses in detail the characteristics and the origin of the major luminescence bands including the ultraviolet, blue, green, yellow, and red bands in undoped GaN. The effects of important group-II impurities, such as Zn and Mg on the photoluminescence of GaN, are treated in detail. Similarly, but to a lesser extent, the effects of other impurities, such as C, Si, H, O, Be, Mn, Cd, etc., on the luminescence properties of GaN are also reviewed. Further, atypical luminescence lines which are tentatively attributed to the surface and structural defects are discussed. The effect of surfaces and surface preparation, particularly wet and dry etching, exposure to UV light in vacuum or controlled gas ambient, annealing, and ion implantation on the characteristics of the defect-related emissions is described.

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Section: Substitutional Acceptorsmentioning

confidence: 99%

Luminescence properties of defects in GaN

Reshchikov¹,

Morkoç̌²

2005

Journal of Applied Physics

1,828

119

1,666

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“…As another example, beryllium diffuses in the c-plane with diffusion energy of 1.2 eV, compared to diffusion energy of 2.9 eV along the c axis. 7 Another consideration is that dislocations may act as sources for native defects, e.g., growth of n-type GaN under gallium rich conditions may encourage formation of either type of vacancy at dislocations, 8 which can then disperse within the crystal if the diffusion energy is low enough. With potentially low and anisotropic diffusion energies, we may expect that some of the defects in GaN are mobile at moderately high temperatures, within device operational range.…”

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confidence: 99%

Thermal stability of electron traps in GaN grown by metalorganic chemical vapor deposition

Johnstone

Doğan

Leach

et al. 2004

Applied Physics Letters

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Deep level transient spectroscopy was used to investigate the thermal stability of electron traps in n-type GaN grown by metalorganic chemical vapor deposition. The concentration of traps at 160 and at 500K increased more than fivefold over the course of several 700K anneal cycles, while a peak at 320K increased by a factor of only 1.19. The increase in the trap concentration with repeated annealing might be due to a mobile trap or loss of passivant. Hydrogen is very likely present in high concentration in the epilayer, and its passivating effects may be lost with annealing.

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“…From the theoretical side, Be is one of the most studied impurities in GaN and considerable efforts have been made in order to understand its doping behavior [4,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. However, up to now no consensus has been reached regarding theoretical predictions of its acceptor level(s), for which values of <200 meV [16], 60 meV [17], 185-241 meV [18], 183-190 meV [20], 60 meV [22], 120 meV [23], 550 meV [25], 47-93 meV [26], 600 meV [28], 720-800 meV [29], and 205 meV [31] can be found in the literature.…”

Section: Introductionmentioning

confidence: 99%

“…One theoretical study [24] and recent experimental results [30] point towards the hypothesis that Be has two acceptor levels, a relatively shallow one (EA≈113 meV), and a second, which is deeper (E A ≈580 meV) and characterized by large lattice relaxations. Moreover, several theoretical studies [4,16,19,[21][22][23]25,31] have predicted that Be is an amphoteric impurity in GaN, meaning that it can occupy substitutional Ga positions (Be Ga ), where it acts as an acceptor, but also interstitial sites (Be i ), where it acts as a double donor. This implies that the formation of interstitial Be i instead of substitutional Be Ga should become more favorable in p-GaN, which was forecast to be the case once the Fermi level is closer than ≈1.2 eV [16], 0.8 eV [19], 0.5 eV [21], 0.3-0.5 eV [22], 1.4-1.8 eV [25], or 1.2-1.6 eV [31] from the valence band.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, several theoretical studies [4,16,19,[21][22][23]25,31] have predicted that Be is an amphoteric impurity in GaN, meaning that it can occupy substitutional Ga positions (Be Ga ), where it acts as an acceptor, but also interstitial sites (Be i ), where it acts as a double donor. This implies that the formation of interstitial Be i instead of substitutional Be Ga should become more favorable in p-GaN, which was forecast to be the case once the Fermi level is closer than ≈1.2 eV [16], 0.8 eV [19], 0.5 eV [21], 0.3-0.5 eV [22], 1.4-1.8 eV [25], or 1.2-1.6 eV [31] from the valence band. The lack of p-type characteristics following Be doping could thus be explained by self-compensation, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Direct evidence of Be as an amphoteric dopant in GaN

et al. 2022

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The interest in Be as an impurity in GaN stems from the challenge to understand why GaN can be doped ptype with Mg, while this does not work for Be. While theory has actually predicted an acceptor level for Be that is shallower than Mg, it was also argued that Be is not a suitable acceptor because its amphoteric nature, i.e. its tendency to occupy substitutional Ga as well as interstitial sites, would be considerably more pronounced than for Mg and hence lead to self-compensation. Using the emission channeling technique at the ISOLDE/CERN facility, we determined the lattice location of 11 Be (t1/2=13.8 s) in different doping types of GaN as a function of implantation temperature. We find within an accuracy of 0.08 Å that the location of interstitial Be is the one predicted by theory. The room temperature interstitial fraction of 11 Be was correlated with the GaN doping type, being highest (up to ~80%) in p-type and lowest in n-GaN, thus giving direct evidence for the amphoteric character of Be. We find that interstitial 11 Be fractions are generally much higher than for Mg, which confirms that indeed self-compensation should be considerably more pronounced for Be. With rising implantation temperature, an increasing conversion of interstitial to substitutional Be is observed, involving at least two clearly identifiable steps at 50-150 °C and 350-500 °C. This suggests that the migration of interstitial Be may be subject to two different activation energies.

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Stability, diffusion, and complex formation of beryllium in wurtzite GaN

Cited by 3 publications

References 9 publications

Luminescence properties of defects in GaN

Luminescence properties of defects in GaN

Thermal stability of electron traps in GaN grown by metalorganic chemical vapor deposition

Direct evidence of Be as an amphoteric dopant in GaN

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