Defects in p-doped bulk GaN crystals grown with Ga polarity

Liliental‐Weber, Z.; Tomaszewicz, T.; Zakharov, Dmitri N.; O’Keefe, Michael A.

doi:10.1016/j.jcrysgro.2005.03.049

Cited by 17 publications

(21 citation statements)

References 27 publications

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“…The similar pyramidal shape defects are earlier observed in Mg-doped GaN films and their existence is usually explained by modification in GaN atomic structure due to Mg introduction [19–24]. Liliental-Weber et al [25, 26] proposed that such pyramidal defects originate from Mg-rich clusters present near the head of these pyramids. The GaN structure in wurtzite phase is usually described by hexagonal stacking of N planes with half of the N sublattice tetrahedra sites filled by Ga atoms.…”

Section: Resultssupporting

confidence: 58%

Comparative Analysis of Defects in Mg-Implanted and Mg-Doped GaN Layers on Freestanding GaN Substrates

et al. 2018

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Inefficient Mg-induced p-type doping has been remained a major obstacle in the development of GaN-based electronic devices for solid-state lighting and power applications. This study reports comparative structural analysis of defects in GaN layers on freestanding GaN substrates where Mg incorporation is carried out via two approaches: ion implantation and epitaxial doping. Scanning transmission electron microscopy revealed the existence of pyramidal and line defects only in Mg-implanted sample whereas Mg-doped sample did not show presence of these defects which suggests that nature of defects depends upon incorporation method. From secondary ion mass spectrometry, a direct correspondence is observed between Mg concentrations and location and type of these defects. Our investigations suggest that these pyramidal and line defects are Mg-rich species and their formation may lead to reduced free hole densities which is still a major concern for p-GaN-based material and devices. As freestanding GaN substrates offer a platform for realization of p-n junction-based vertical devices, comparative structural investigation of defects originated due to different Mg incorporation processes in GaN layers on such substrates is likely to give more insight towards understanding Mg self-compensation mechanisms and then optimizing Mg doping and/or implantation process for the advancement of GaN-based device technology.

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Section: Resultssupporting

confidence: 58%

Comparative Analysis of Defects in Mg-Implanted and Mg-Doped GaN Layers on Freestanding GaN Substrates

et al. 2018

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“…We further speculate that these hexagons might be related to the presence of Mg, as found earlier in GaN:Mg samples [27,[31][32][33][34][35], although the Mg concentration is much lower (~4x10 16 cm --3 ) in Sample B compared to samples described in the above references (~1x10 19 cm --3 ). However, the non-uniform distribution of these hexagons may indicate that there are regions (in sub-micron size) with locally higher Mg in this sample that cannot be detected by SIMS.…”

Section: Cross-sectional and Plan-view Tem Studiessupporting

confidence: 73%

“…Tilting of the plan-view samples confirm that these hexagonal features are inverted pyramids. The presence of such features would suggest either the formation of pinholes protruding through the sample surface [27][28][29][30] or pyramidal inversion domains similar to those formed in highly Mg doped GaN samples [27,[31][32][33][34][35]. Such pinholes were observed earlier in samples with a high impurity density, especially with oxygen [28], where pinholes were formed not only at dislocations but also in dislocation free areas.…”

Section: Cross-sectional and Plan-view Tem Studiesmentioning

confidence: 99%

The importance of structural inhomogeneity in GaN thin films

Liliental‐Weber

Reis

Weyher

et al. 2016

Journal of Crystal Growth

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This paper describes two types of MOCVD-grown n-type GaN layers (Samples A and B) with similar carrier concentration but behaved differently under galvanic photoetching. In order to understand this behavior, Transmission Electron Microscopy (TEM) for cross-section and plan-view samples, Secondary Ion Mass Spectroscopy (SIMS) and photoluminescence (PL) techniques were applied. SIMS studies showed that Si, C and O are approximately at the same concentration in both samples, but sample B also contained Fe and Mg. Both GaN samples were grown on sapphire substrate with Ga growth polarity, which was confirmed by Convergent Beam Electron Diffraction (CBED). Despite a smaller layer thickness in Sample B, the density of edge dislocations is almost one order of magnitude lower than in Sample A. In addition, planar defects formed in this sample in the transition area between the undoped buffer and Si doped layers resulted in a substantial decrease in the density of screw dislocations at the sample surface. These planar defects most probably gave rise to the PL lines observed at 3.42 eV and 3.32 eV. The new PL lines that only appeared in Sample B might be related to Mg impurities found in this sample. There were no detectable gettering of these impurities at dislocations using different diffraction conditions. However, Fe rich platelets were found only in Sample B due to the presence of Fe as well as hexagonal features, similar to defects reported earlier in highly Mg-doped GaN. These structural and chemical nonuniformities between the two GaN samples can explain their different etching behaviors. This paper demonstrates that samples with similar carrier concentrations do not necessarily ensure similar structural and optical properties and that additional material characterization are needed to ensure that devices built on such samples have similar performance.

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“…These defects have been studied in the literature and different models were suggested to explain their nature, all of them comprise an enrichment of Mg in the boundary or inside the PDs. Hansen et al [1] stated that the PDs are antibixbyite (Mg 3 N 2 ) precipitates, whereas Liliental-Weber et al [2][3][4][5] observed cavities inside PDs and assert that in the PDs the boundaries are decorated by Mg and covered by GaN of reversed polarity. Vennéguès et al [6] studied Mg doped bulk GaN grown by high-pressure, high-temperature method exhibiting rather large PDs with basal plane diameters of ∼100 nm.…”

Section: Introductionmentioning

confidence: 99%

Structural analysis of pyramidal defects in Mg‐doped GaN

Pretorius

Schowalter

Daneu

et al. 2006

Phys. Status Solidi (c)

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Pyramidal defects in GaN:Mg grown by metalorganic vapour phase epitaxy are studied by high resolution transmission electron microscopy, energy dispersive X-ray analysis and scanning transmission electron microscopy. High resolution transmission electron microscopy images were simulated using the multislice approach in order to analyse the basal plane of the pyramidal defects. The simulated images were compared quantitatively with the experimental images. Two structural models for the basal plane inversion domain boundary containing antibixbyite-type layers are presented which show the best observed agreement with the experimentally found inversion domain boundary. Nevertheless, both models still do not match the experimental images satisfactorily, indicating that some other structure than antibixbyite is present at the boundary.

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Defects in p-doped bulk GaN crystals grown with Ga polarity

Cited by 17 publications

References 27 publications

Comparative Analysis of Defects in Mg-Implanted and Mg-Doped GaN Layers on Freestanding GaN Substrates

Comparative Analysis of Defects in Mg-Implanted and Mg-Doped GaN Layers on Freestanding GaN Substrates

The importance of structural inhomogeneity in GaN thin films

Structural analysis of pyramidal defects in Mg‐doped GaN

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