Stephen W. Bedell, S. Hart, et al.
PRiME 2020
Successful wafer-scale layer transfer from high-quality 2-in. diameter bulk gallium nitride substrates was demonstrated using the Controlled Spalling technique. The crystal quality of both the as-fractured bulk substrate and the spalled GaN film was assessed using transmission electron microscopy analysis, and the defect density was below the detection limit (mid 107 cm-2) for both samples. By using the experimentally determined critical conditions for tensile stress and thickness of the Ni stressor layer, an effective fracture toughness KIC of 1.7 MPa m could be calculated for [0001] fracture using the Suo and Hutchinson mechanical model. The resulting in-plane contraction of the GaN film after spalling permitted a novel method for measuring film strain without knowledge of the elastic properties of the material. This was used to measure the Raman E2(high) peak shift coefficient of Δω(cm-1) = 1411ϵ which, when converted to a stress coefficient (2.95 cm-1/GPa), was in agreement with only one other literature value.
Stephen W. Bedell, S. Hart, et al.
PRiME 2020
Ning Li, Kevin Han, et al.
Nature Photonics
Shu Jen Han, Jianshi Tang, et al.
Nature Nanotechnology
Christos Dimitrakopoulos, Yu-Ming Lin, et al.
Journal of Vacuum Science and Technology B