Interfacial adhesion strength of III-N heterostructures

Wide bandgap semiconductors such as group III-nitrides and SiC are considered as key materials for the fabrication of smaller, more reliable and efficient power electronics. Fabrication of robust and durable power devices requires an optimized design based on the understanding of the interfacial adhesion properties of the constituent thin-film heterostructures. In this study, the adhesion properties of GaN/AlN layers grown on Si substrates were investigated. Particularly, the influence of the AlN buffer layers, necessary for GaN growth on Si, on the delamination response was determined. The interfacial adhesion strength was obtained using cross-sectional nanoindentation (CSN) and four-point bending (4PB) tests. Analytical models based on beam- and elastic plate theory which were applied respectively to calculate the interfacial fracture energy (Gic) for both methods are found to be in good agreement provided the loading conditions are similar. Detailed transmission and scanning electron microscopy investigations prior and subsequent to delamination reveal the microstructural details of the relevant interfaces and provide insights into the encountered mechanisms of interfacial failure. Finally, the probability of delamination along the weakest interface is discussed based on a fracture mechanics model.