Nanoindentation-Induced Structural Deformation in GaN/AIN Multilayers

Abstract

The mechanical responses of GaN/AIN multilayers grown on Si(111) substrates by using the metal-organic vapor phase epitaxy (MOVPE) were investigated by combining the Berkovich nanoindentation and the cross-sectional transmission electron microscopy (XTEM) techniques. The prominent mechanical parameters such as the hardness and Young's modulus of GaN/AIN multilayers were obtained to be 21.6 +/- 0.8 GPa and 285.7 +/- 12.1 GPa, respectively by operating the Berkovich nanoindenter with the continuous contact stiffness measurements (CSM) mode. The structural deformation behaviors were delineated by XTEM observations taken in the vicinity regions just underneath the indenter tip. It was revealed that the "pop-ins" observed in the load displacement curve during loading are due primarily to the activities of dislocation nucleation and propagation. There is no evidence of either phase transformation or micro-crack formation observed in XTEM images of GaN/AIN multilayers, which is consistent with no distinct "pop-out" event displayed in unloading curves.