Low temperature p- type doping of (Al)GaN layers using ammonia molecular beam epitaxy for InGaN laser diodes

Applied Physics Letters

Malinverni

et al. 2016

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We grew heavily Mg-doped GaN using ammonia molecular-beam epitaxy. The use of low growth temperature (740 °C) allows decreasing the incorporation of donor-like defects (<3 × 1017 cm−3) responsible for p-type doping compensation. As a result, a net acceptor concentration of 7 × 1019 cm−3 was achieved, and the hole concentration measured by Hall effect was as high as 2 × 1019 cm−3 at room temperature. Using such a high Mg doping level, we fabricated GaN backward diodes without polarization-assisted tunneling. The backward diodes exhibited a tunneling-current density of 225 A/cm2 at a reverse bias of −1 V at room temperature.

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confidence: 97%

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confidence: 99%

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Backward diodes using heavily Mg-doped GaN growth by ammonia molecular-beam epitaxy

Okumura

Applied Physics Letters

Malinverni

et al. 2016

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“…The specific growth method, morphology, and electrical properties of samples prepared using this method are described elsewhere. 14,27 Sidoped (0001) GaN(4 lm)/sapphire templates were prepared using MOVPE, and they were used as templates. Using NH 3 -MBE, after deposition of a 0.5-lm-thick undoped GaN buffer layer on the templates, Mg-doped GaN layers were grown.…”

Section: à3mentioning

confidence: 99%

Vacancy-type defects in Mg-doped GaN grown by ammonia-based molecular beam epitaxy probed using a monoenergetic positron beam

Uedono

Malinverni

Journal of Applied Physics

et al. 2016

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Vacancy-type defects in Mg-doped GaN were probed using a monoenergetic positron beam. GaN films with a thickness of 0.5–0.7 μm were grown on GaN/sapphire templates using ammonia-based molecular beam epitaxy and characterized by measuring Doppler broadening spectra. Although no vacancies were detected in samples with a Mg concentration [Mg] below 7 × 1019 cm−3, vacancy-type defects were introduced starting at above [Mg] = 1 × 1020 cm−3. The major defect species was identified as a complex between Ga vacancy (VGa) and multiple nitrogen vacancies (VNs). The introduction of vacancy complexes was found to correlate with a decrease in the net acceptor concentration, suggesting that the defect introduction is closely related to the carrier compensation. We also investigated Mg-doped GaN layers grown using In as the surfactant. The formation of vacancy complexes was suppressed in the subsurface region (≤80 nm). The observed depth distribution of defects was attributed to the thermal instability of the defects, which resulted in the introduction of vacancy complexes during the deposition process.

“…Recently, we achieved p-type GaN layers with low compensation defects, i.e., less than 3 Â 10 17 cm À3 and high N A -N D (7 Â 10 19 cm À3 ) by growing GaN:Mg at low temperature using ammonia MBE. 18,19 Such high doping levels should enable very low p-type contact resistance.…”

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confidence: 99%

Low p-type contact resistance by field-emission tunneling in highly Mg-doped GaN

Okumura

Applied Physics Letters

Grandjean

2016

Mg-doped GaN with a net acceptor concentration (NA-ND) in the high 1019 cm−3 range was grown using ammonia molecular-beam epitaxy. Electrical properties of NiO contact on this heavily doped p-type GaN were investigated. A potential-barrier height of 0.24 eV was extracted from the relationship between NA-ND and the specific contact resistivity (ρc). We found that there is an optimum NA-ND value of 5 × 1019 cm−3 for which ρc is as low as 2 × 10−5 Ω cm2. This low ρc is ascribed to hole tunneling through the potential barrier at the NiO/p+-GaN interface, which is well accounted for by the field-emission model.