Selective photoetching and transmission electron microscopy studies of defects in heteroepitaxial GaN

Weyher, J.L.; Tichelaar, F.D.; Zandbergen, H.W.; Macht, L.; Hageman, P.R.

doi:10.1063/1.1416137

Cited by 54 publications

(32 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Photo-etching of the exact oriented sample (Fig. 5a) reveals the dislocations in the form of whiskers, the density (2.5 × 10 9 cm -2 ) of which is a direct measure of the density of dislocations in the GaN epitaxial layers as was demonstrated by calibration of the etch features with cross-sectiona [19,21] and plan-view [22] transmission electron microscopy. However, the GaN layer deposited on the 8° off-orientated substrate shows elongated features instead of whiskers ( Fig.…”

Section: Defect Distributionmentioning

confidence: 99%

Defect formation in GaN grown on vicinal 4H‐SiC (0001) substrates

Rudziński¹,

Jezierska

Weyher

et al. 2007

Physica Status Solidi (a)

Self Cite

View full text Add to dashboard Cite

We report a comparative study of wurtzite GaN epilayers prepared by Metal Organic Chemical Vapor Deposition on 4H-SiC substrates of orientation vicinal to the (0001) (misorientation 0°, 3.4°, and 8°). Structural analysis using X-ray diffraction, defect-selective etching methods, and (High Resolution-) Transmission Electron Microscopy provides direct evidence for a higher number of defects in GaN epilayers grown on the 8° misoriented substrate compared to the 3.4° and 0° misoriented substrates. We found strong differences in morphology of the GaN epilayers and in type and density of the defects formed during growth on both vicinal and nominally exact oriented SiC substrates. The formation of clusters of defects and the non-uniform distribution of strain, resulting in preferential cracking of the GaN films along the [1120] direction, are both results of growth on misoriented substrates. Based on experimental results, the growth mechanism is discussed and a model explaining the defect formation is proposed.

show abstract

Section: Defect Distributionmentioning

confidence: 99%

Defect formation in GaN grown on vicinal 4H‐SiC (0001) substrates

Rudziński¹,

Jezierska

Weyher

et al. 2007

Physica Status Solidi (a)

Self Cite

View full text Add to dashboard Cite

show abstract

“…Two approaches are usually employed for this purpose, namely (i) comparison of dislocation density established by TEM with the density of etch pits (etch features), e.g. [9] and (ii) examination of thin foils prepared from the etched samples using either conventional cross-section specimens [6,10] or focus ion beam (FIB) [12]. For calibration of the orthodox etching method, which reveals dislocations in the form of pits, the latter approach is the most favorable because it yields a direct association of the etch feature with the underlying defect.…”

Section: Introductionmentioning

confidence: 99%

“…: direct calibration by X-ray topography [1] (suitable for dislocation density below 10 5 cm -2 ), comparison with cathodoluminescence (CL) [2], electron beam induced current (EBIC) [3] or another calibrated etching method [4], sequent etching [5] and calibration by TEM, as in e.g. [4][5][6][7][8]. Among these methods the latter is the most attractive because it offers the possibility of establishing not only the one-to-one correspondence between the etch features and the individual defects but also to establish a correlation between different features and their causative defects.…”

Section: Introductionmentioning

confidence: 99%

Orthodox etching of HVPE-grown GaN

Weyher

Lazar

Macht

et al. 2007

Journal of Crystal Growth

Self Cite

116

103

View full text Add to dashboard Cite

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.

show abstract

“…1 However, regions of enhanced emission have also been observed by cross-sectional CL and attributed to decorated dislocations. 2 Previous investigations [3][4][5] indicate that threading dislocations in n-GaN can be visualized by the formation of whiskers during photoelectrochemical ͑PEC͒ etching. The high resistance of whiskers to PEC attack was attributed to the negative charge inherent to threading dislocations in n-GaN.…”

mentioning

confidence: 99%

Spatially resolved cathodoluminescence of GaN nanostructures fabricated by photoelectrochemical etching

Dı́az-Guerra

Piqueras

Popa

et al. 2005

Applied Physics Letters

View full text Add to dashboard Cite

The emission properties of GaN nanostructures created by photoelectrochemical etching have been investigated by cathodoluminescence (CL) in the scanning electron microscope. Columnar structures with diameters of 150–250 nm formed near the surface of the as-grown GaN layers branch into nanowires with diameters of 20–60 nm, while islands with coral-like relief were observed at the bottom of the etched areas. CL emission of the observed nanostructures is dominated by free electron to acceptor transitions. Local CL spectra provide direct evidence of the existence of either compressive or tensile stress in different nanostructures. No free exciton luminescence was observed in GaN nanowires, supporting their relation to threading dislocations.

show abstract

Selective photoetching and transmission electron microscopy studies of defects in heteroepitaxial GaN

Cited by 54 publications

References 39 publications

Defect formation in GaN grown on vicinal 4H‐SiC (0001) substrates

Defect formation in GaN grown on vicinal 4H‐SiC (0001) substrates

Orthodox etching of HVPE-grown GaN

Spatially resolved cathodoluminescence of GaN nanostructures fabricated by photoelectrochemical etching

Contact Info

Product

Resources

About