Elastic and plastic properties of GaN determined by nano-indentation of bulk crystal

Abstract

The major obstacle to the production of a blue laser is posed by difficulties with the preparation of defect-free GaN layers. A considerable amount of empirical work is presently being undertaken to achieve this goal. However, there is a lack of basic research on the reduction of residual stress and defects in these epilayers since the mechanical characteristics of GaN have not been measured yet. This is due to difficulties with experimental examination of thin films. This work addresses the mechanical properties of bulk GaN obtained by a high-pressure method. Young’s modulus (295 GPa), hardness (20 GPa), yield strength (15 GPa), and the stress–strain curve of GaN have been evaluated using nano-indentation. The cause of the sudden depth excursions during indentation of GaN epilayers has been clarified.

Yield shear stress dependence on nanoindentation strain rate in bulk GaN crystal

“…In order to obtain the critical load P crit dependence on strain rate, the indentation velocity v was ranged from 0.16 nm/s to 800 nm/s with constant temperature T = 300 K. Young's modulus E, hardness H and maximum shear stress τ max were calculated by following the Ref. [3,4].…”

“…The most articles in the past studies have investigated the mechanical properties of multilayered GaN crystals on the sapphire substrate [3] and there are a few articles which investigated that of bulk GaN crystals [4], because these bulk GaN crystals were developed quite recent years and they are still scarce materials now. We selected bulk GaN crystals for current study in order to determine the precise mechanical responses, and we applied the nanoindentation technique which is increasingly serving a significant role of revealing the material physical properties in recent years [5][6][7][8][9][10][11][12][13].…”

Mechanical properties characterization of c ‐plane (0001) and m ‐plane (10–10) GaN by nanoindentation examination

“…The detail calculation procedure for the indenter curvature radius was described in Ref. [13,14]. Penetration depth h was registered with using each indenter, while the load P applied up to P max was equal to 5 mN (0.51 gf) or 9 mN (0.92 gf).…”

Electronic and optical properties of quantum wells embedded in wrinkled nanomembranes

“…[18][19] The maximum bandwidth can be estimated by For example, if we scale up the wrinkle dimensions to…”