Orthodox etching of HVPE-grown GaN

• Published in: Journal of crystal growth Vol. 305; no. 2; pp. 384 - 392
• Main Authors: Weyher, J.L., Lazar, S., Macht, L., Liliental-Weber, Z., Molnar, R.J., Müller, S., Sivel, V.G.M., Nowak, G., Grzegory, I.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15-07-2007; Elsevier
• Subjects: A1. Defects; A1. Etching; Applied sciences; B1. Nitrides; Cross-disciplinary physics: materials science; rheology; Design. Technologies. Operation analysis. Testing; Electronics; Exact sciences and technology; Integrated circuits; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Microelectronic fabrication (materials and surfaces technology); Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Vapor phase epitaxy; growth from vapor phase; B1. Nitrides; A1. Etching; A1. Defects; Phosphoric acid; Bl. Nitrides; Deformation; Al. Defects; VPE; Edge dislocation; Calibration; Gallium nitride; III-V compound; Optimization; Burgers vector; Sulfuric acid; Nitrides; Microelectronic fabrication; Engraving; Transmission electron microscopy; Al. Etching; Threading dislocation; Experimental design; Eutectic; Reliability; III-V semiconductors
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2007.03.030

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.