Surface polarity dependence of Mg doping in GaN grown by molecular-beam epitaxy

Li, L. K.; Jurkovic, M. J.; Wang, W. I.; Hove, J. M. Van; Chow, P. P.

doi:10.1063/1.126152

Cited by 105 publications

(71 citation statements)

References 18 publications

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“…20 Thus, these results demonstrate that under identical growth conditions, net Mg acceptor incorporation is more efficient for Ga-face compared to N-face material. This observation is consistent with prior reports that Mg doping of GaN results in greater total Mg incorporation 8 and higher p-type conductivity 21 for material grown with Ga-face polarity compared to N-face material and suggests that avoidance of inversion domain formation is essential for optimization of p-type conductivity in GaN. In addition to revealing higher net Mg acceptor incorporation into Ga-face compared to N-face material, SCM imaging indicates that higher net concentrations of ionized Mg acceptors can occasionally be present in the immediate vicinity of inversion domain boundaries than in the surrounding Ga-face and N-face materials.…”

Section: ͑3͒supporting

confidence: 82%

Dependence of local electronic structure in p-type GaN on crystal polarity and presence of inversion domain boundaries

Zhou

Green

et al. 2006

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Scanning probe techniques including scanning capacitance microscopy, scanning capacitance spectroscopy, scanning Kelvin probe force microscopy, and atomic force microscopy have been used to assess structure and local electronic properties of Ga-face and N-face p-type GaN and of inversion domain boundaries in p-type GaN. Epitaxial layers of p-type GaN were grown by molecular-beam epitaxy, and by adjustment of the Ga:N flux ratio samples containing both Ga-face and N-face material were obtained. Under identical growth conditions, net incorporation of electrically active Mg acceptors was found to be more efficient for material with Ga-face polarity. Only a very small dependence of surface potential on polarity was observed, in contrast to results reported for n-type GaN, in which a substantial dependence of Schottky barrier height on polarity has been found. In addition, elevated net concentrations of ionized Mg acceptors were observed in Ga-face regions in the immediate vicinity of some, but not all, inversion domain boundaries, consistent with theoretical suggestions that incorporation of high concentrations of Mg within an inversion domain boundary can lead to increased concentrations of Mg acceptors near the inversion domain boundary.

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Section: ͑3͒supporting

confidence: 82%

Dependence of local electronic structure in p-type GaN on crystal polarity and presence of inversion domain boundaries

Zhou

Green

et al. 2006

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…In general, besides the orientation of the Ga-N bonds, there is no crystal structure difference between the Ga-polar and N-polar GaN nanorods. However, different polar surfaces induce different surface chemical reactivity, which is important, e.g., in the case of the impurity doping, 55,56 dopant incorporation, 57,58 surface reaction with gas, 59 and growth morphology of the GaN nanorods. 39,42 There are already numerous investigations reported on two-dimensional GaN layers with different polarities concerning these topics.…”

Section: B Catalyst-free Gan Nanorod Growthmentioning

confidence: 99%

GaN based nanorods for solid state lighting

Li¹,

Waag

2012

Journal of Applied Physics

488

394

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In recent years, GaN nanorods are emerging as a very promising novel route toward devices for nano-optoelectronics and nano-photonics. In particular, core-shell light emitting devices are thought to be a breakthrough development in solid state lighting, nanorod based LEDs have many potential advantages as compared to their 2 D thin film counterparts. In this paper, we review the recent developments of GaN nanorod growth, characterization, and related device applications based on GaN nanorods. The initial work on GaN nanorod growth focused on catalyst-assisted and catalyst-free statistical growth. The growth condition and growth mechanisms were extensively investigated and discussed. Doping of GaN nanorods, especially p-doping, was found to significantly influence the morphology of GaN nanorods. The large surface of 3 D GaN nanorods induces new optical and electrical properties, which normally can be neglected in layered structures. Recently, more controlled selective area growth of GaN nanorods was realized using patterned substrates both by metalorganic chemical vapor deposition (MOCVD) and by molecular beam epitaxy (MBE). Advanced structures, for example, photonic crystals and DBRs are meanwhile integrated in GaN nanorod structures. Based on the work of growth and characterization of GaN nanorods, GaN nanoLEDs were reported by several groups with different growth and processing methods. Core/shell nanoLED structures were also demonstrated, which could be potentially useful for future high efficient LED structures. In this paper, we will discuss recent developments in GaN nanorod technology, focusing on the potential advantages, but also discussing problems and open questions, which may impose obstacles during the future development of a GaN nanorod based LED technology.

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“…Li et al investigated the impact of polarity by changing the nucleation conditions in direct MBE growth on sapphire prior to Mg doping. 18 Li et al found that Mg-doped N-face films have higher defect densities and are more resistive than the p-type films achievable for Ga-face growth. Beyond simply preventing undesirable polarity inversion, understanding the mechanism responsible for inversion allows the potential for controllably changing polarity in a single epitaxial growth.…”

mentioning

confidence: 99%

Polarity control during molecular beam epitaxy growth of Mg-doped GaN

Green

Haus

et al. 2003

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Mg doping has been found in some situations to invert growth on Ga-face GaN to N-face. In this study, we clarified the role the Ga wetting layer plays in rf plasma molecular beam epitaxy of GaN when Mg doping, for [Mg] from ∼2×1019 to ∼1×1020 cm−3 corresponding to the useful, accessible range of hole concentrations of p∼1017–1018 cm−3. Structures were grown in the N-rich and Ga-rich growth regime for single Mg doping layers and for multilayer structures with a range of Mg concentrations. Samples were characterized in situ by reflection high-energy electron diffraction and ex situ by atomic force microscopy, transmission electron microscopy, convergent beam electron diffraction, and secondary ion mass spectroscopy. Growth on “dry” surfaces (without a Ga wetting layer) in the N-rich regime completely inverted to N-face upon exposure to Mg. No reinversion to Ga-face was detected for subsequent layers. Additionally, Mg was seen to serve as a surfactant during this N-rich growth, as has been reported by others. Growth initiated in the Ga-rich regime contained inversion domains that nucleated with the initiation of Mg doping. No new inversion domains were found as the Mg concentration was increased through the useful doping levels. Thus the Ga wetting layer was found to inhibit nucleation of N-face GaN, though a complete wetting layer took time to develop. Finally, by establishing a complete Ga wetting layer on the surface prior to growth, we confirmed this finding and demonstrated Mg-doped GaN completely free from inversion domains to a doping level of [Mg]∼2×1020.

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Surface polarity dependence of Mg doping in GaN grown by molecular-beam epitaxy

Cited by 105 publications

References 18 publications

Dependence of local electronic structure in p-type GaN on crystal polarity and presence of inversion domain boundaries

Dependence of local electronic structure in p-type GaN on crystal polarity and presence of inversion domain boundaries

GaN based nanorods for solid state lighting

Polarity control during molecular beam epitaxy growth of Mg-doped GaN

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