Wet Chemical Etching of AlN Single Crystals
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Wet Chemical Etching of AlN Single Crystals D. Zhuang, J.H. Edgar, Lianghong Liu, B. Liu and L. Walker MRS Internet Journal of Nitride Semiconductor Research / Volume 7 / January 2002 DOI: 10.1557/S1092578300000302, Published online: 13 June 2014
Link to this article: http://journals.cambridge.org/abstract_S1092578300000302 How to cite this article: D. Zhuang, J.H. Edgar, Lianghong Liu, B. Liu and L. Walker (2002). Wet Chemical Etching of AlN Single Crystals . MRS Internet Journal of Nitride Semiconductor Research, 7, pp e4 doi:10.1557/S1092578300000302 Request Permissions : Click here
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MRS
Internet Journal Nitride Semiconductor Research
Wet Chemical Etching of AlN Single Crystals D. Zhuang1, J.H. Edgar1, Lianghong Liu1, B. Liu1 and L. Walker2 1Department 2Metals
of Chemical Engineering, Kansas State University, and Ceramics Division, Oak Ridge National Laboratory,
(Received Tuesday, May 7, 2002; accepted Sunday, June 16, 2002)
Anisotropic chemical etching is an important means for characterizing the polarity and defect density of single crystals. In this letter, we present the results of our studies on the etching of bulk AlN crystals in aqueous potassium hydroxide solution. The nitrogen polarity (0001) basal plane initially etched rapidly, while the aluminum polarity basal plane, and prismatic (1100) planes were not etched. The etch rate of the nitrogen polarity basal plane eventually decreased to zero, as the surface became completely covered with hexagonal hillocks which were bounded by {1101} planes. The hillock density for the self-seeded AlN crystals studied was typically in the range of 5×107 cm2 to 109 cm-2. From our analysis of etched AlN crystals, we infer that freely nucleated crystals predominately have the nitrogen to aluminum direction pointing out from the nucleation surface, that is the ends of the AlN crystals facing the source are aluminum polarity.
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Introduction
GaN has attracted vast interest due to its unique properties and potential applications in optoelectronic and microelectronic devices. However, the dislocation density in GaN heteroepitaxial layers as high as 108 cm-2 [1] shortens the lifetime of GaN based devices. The chemical compatibility and lattice/thermal expansion match between AlN and GaN make bulk AlN single crystals potentially suitable for GaN epitaxial growth. In addition, the high thermal conductivity (340W/m·K) and high electrical resistivity make AlN ideal for high power devices [2]. Recently, several groups [3] [4] [5] have reported growth of relatively large AlN single crystals, typically at millimeter square scale, produced by the sublimation process, originating from Slack and McNelly's work in 1970s [6]. Understanding the sublimation growth process and the quality of the AlN crystals it produces is key to p
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