Hardness of bulk single-crystal GaN and AlN
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Hardness of bulk single-crystal GaN and AlN Ichiro Yonenaga MRS Internet Journal of Nitride Semiconductor Research / Volume 7 / January 2002 DOI: 10.1557/S1092578300000326, Published online: 13 June 2014
Link to this article: http://journals.cambridge.org/abstract_S1092578300000326 How to cite this article: Ichiro Yonenaga (2002). Hardness of bulk single-crystal GaN and AlN . MRS Internet Journal of Nitride Semiconductor Research, 7, pp e6 doi:10.1557/S1092578300000326 Request Permissions : Click here
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MRS
Internet Journal Nitride Semiconductor Research
Hardness of bulk single-crystal GaN and AlN Ichiro Yonenaga1 1Institute
for Materials Research, Tohoku University,
(Received Friday, August 9, 2002; accepted Wednesday, September 18, 2002)
The hardness of single-crystal GaN and AlN of 0.5-mm-thickness was measured by the Vickers indentation method in the temperature range 20 - 1400°C. The hardness of GaN and AlN is 10.2 and 17.7 GPa, respectively, at room temperature. The nano-indentation hardness of single-crystal AlN was measured at room temperature as 18 GPa, harder than GaN and InN. Up to about 1100°C, GaN and AlN maintain its hardness similar to that of SiC and thus, a high mechanical stability for GaN and AlN at elevated temperatures is deduced. Yield strength of nitrides is discussed.
1
Introduction
III-V nitrides are finding applications such as in highpower/high-frequency devices, high-power switches, blue and ultraviolet light-emitting devices/photo-detectors, and chemically stable substrates for various materials. Many of the physical properties required for characterizing the material have been determined in the past, however, up to now, comparatively little is known about the mechanical properties of these materials. Mechanical characteristics such as elastic constants, yield strength at elevated temperatures, etc. are crucial for controlling dislocation generation and plastic deformation during crystal growth and device processing. The reduction in dislocation density is expected to result in improvement of the optical and electrical performance of nitrides. It is also necessary to solve the problems of residual stress/strain for the potential optical and electronic properties in a device design. A considerable effort has already been made to evaluate the elastic stiffness coefficients of nitride by ab-inito calculations [1] [2] [3]. The difficulty of preparation of bulk III-V nitride crystals was a limiting factor in obtaining this information. Recently, some research groups have succeeded in growing thick nitride films, which can be regarded as a bulk material, by using a hydride vapor phase epitaxy (HVPE) technique [4] [5]. Hardness is a material parameter indicating resistance to elastic/plastic deformation. Thus, various indentation ha
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