Origin of hexagonal-shaped etch pits formed in (0001) GaN films

Hong, Soon–Ku; Yao, Takafumi; Kim, B. J.; Yoon, Seon‐Jin; Kim, T. I.

doi:10.1063/1.126884

Cited by 106 publications

(57 citation statements)

References 17 publications

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“…The attempts to attribute the size of pits to the type of dislocations showed unambiguously that the largest pits are formed on nano-pipes, i.e. open core screw dislocations [11,14,15]. Different morphologies of pits formed on edge, mixed and screw dislocations were reported after etching of GaN in HCl at 600 °C [16], while after etching in molten KOH Shiojima [12] found larger pits on mixed and smaller ones on edge dislocations.…”

Section: Introductionmentioning

confidence: 99%

Orthodox etching of HVPE-grown GaN

Weyher

Lazar

Macht

et al. 2007

Journal of Crystal Growth

116

103

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Orthodox etching of HVPE-grown GaN in molten eutectic of KOH + NaOH (E etch) and in hot sulfuric and phosphoric acids (HH etch) is discussed in detail. Three size grades of pits are formed by the preferential E etching at the outcrops of threading dislocations on the Ga-polar surface of GaN. Using transmission electron microscopy (TEM) as the calibration tool it is shown that the largest pits are formed on screw, intermediate on mixed and the smallest on edge dislocations. This sequence of size does not follow the sequence of the Burgers values (and thus the magnitude of the elastic energy) of corresponding dislocations. This discrepancy is explained taking into account the effect of decoration of dislocations, the degree of which is expected to be different depending on the lattice deformation around the dislocations, i.e. on the edge component of the Burgers vector. It is argued that the large scatter of optimal etching temperatures required for revealing all three types of dislocations in HVPE-grown samples from different sources also depends upon the energetic status of dislocations. The role of kinetics for reliability of etching in both etches is discussed and the way of optimization of the etching parameters is shown.

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Section: Introductionmentioning

confidence: 99%

Orthodox etching of HVPE-grown GaN

Weyher

Lazar

Macht

et al. 2007

Journal of Crystal Growth

116

103

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“…However, in order to achieve this goal, the optimal ratio between temperature and time of etching has to be established for the given density/type of defects in the etched material. This approach is a prerequisite for avoiding controversial conclusions of some previous reports [22,23]. Etching in E+M is a universal method: it can be used both for pure GaN as well as for other III-N (e.g.…”

mentioning

confidence: 98%

Characterization of GaN single crystals by defect‐selective etching

Weyher

Macht

Kamler

et al. 2003

phys. stat. sol. (c)

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In this communication it is shown that both "orthodox" etching in molten KOH -NaOH eutectic (E etch and its modification) and photo-etching in aqueous KOH solution (PEC method) permit quick assessment of density, distribution and, after appropriate calibration, type of defects in GaN single crystals and epitaxial layers. Characteristic features of both etching methods are briefly discussed. It is shown that dislocations and micro-defects can be revealed in the form of etch pits (in "orthodox" E etch) and as etch hillocks (PEC method) on both Ga-and N-polar surfaces. The reliability of both methods has been confirmed by direct TEM calibration and by using indentation method. Very low dislocation density (EPD ≤ 2 × 10 2 cm −2 ) in the undoped GaN single crystals and MOCVD-grown epitaxial layers has been confirmed by this study.Introduction High-pressure grown GaN single crystals constitute an attractive substrate material for manufacturing lattice matched (i.e. low defect-density) high performance III-V opto-electronic device structures [1][2][3]. At the early stage of the development of sizable GaN single crystals and homo-epitaxial layers, the structural quality of the material was determined using X-ray diffraction [4-6] and transmission electron microscopy (TEM) [7][8][9]. These techniques demonstrated superior quality of the GaN single crystals and the layers grown on them over hetero-epitaxial layers, but failed in precise determining of the density of dislocations due to the intrinsic limits of the methods.More recently, the structural quality of GaN crystals and epitaxial layers has been examined by defectselective etching [10][11][12]. The delay in using simple and quick etching vs. X-ray and TEM, has been caused by the very high chemical resistance of nitrides. From the recent studies it follows however, that two approaches are the most promising in revealing and analysing defects in different types of GaN, namely photo-electrochemical (PEC or electroless) [12][13][14] and molten bases [11,15] etching. In the present communication these two techniques are briefly characterized and some representative examples are shown on the use of these methods for studying defects in GaN single crystals and epitaxial layers.

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“…These volumes 6 cm -2 . This density was similar to the typical density of the screw dislocation of GaN grown by MOVPE [11,12]. From this consideration, GaN was prior to dissolve from the surroundings of screw dislocation with the bias over +0.4 V vs CE.…”

Section: Time Variations Of Photocurrent With Different Applied Biasmentioning

confidence: 95%

Time variation of GaN photoelectrochemical reactions affected by light intensity and applied bias

Koike

Sato

Fujii

et al. 2010

Phys. Status Solidi (c)

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We investigated photoelectrochemical reactions affected by light intensity and applied bias using GaN. Time variations of the photocurrent changed with the photo‐illuminated intensity and the applied bias. The bias application affected the time variation much, and the bias under +0.2 V vs counterelectrode for n‐type GaN is good for the continuous reaction. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Origin of hexagonal-shaped etch pits formed in (0001) GaN films

Cited by 106 publications

References 17 publications

Orthodox etching of HVPE-grown GaN

Orthodox etching of HVPE-grown GaN

Characterization of GaN single crystals by defect‐selective etching

Time variation of GaN photoelectrochemical reactions affected by light intensity and applied bias

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