Suspended-ultrathin Si membrane on SOI: a novel structure to reduce thermal stress of GaN epilayer

Abstract A 30nm-thick suspended-ultrathin silicon membrane based on SOI (silicon-on-insulator) substrate for GAN epitaxial growth is fabricated and analysed. We demonstrate that thermal stress of GaN in the effective area on this novel substrate can be reduced 44% more than that in normal SOI substrate, which can reduce the dislocation and crack density in GaN. The absence of BOX (buried oxide) layer are confirmed as main factors to result in reduction of thermal stress in GaN layer. This work provides a promising approach to obtain high-quality GaN by utilizing mechanical structure.