N-face GaN/AlGaN Transistors Through Substrate Removal

In this paper, we present a new method to fabricate N-face GaN/AlGaN HEMTs based on the substrate removal of a Ga-face AlGaN/GaN layer grown on Si. A new substrate removal and transfer technology with no degradation to the GaN active layer. This technology has allowed the fabrication of N-face GaN transistors with record sheet resistance values. The Ga-face surface was bonded to a Si carrier wafer by using a hydrogen silsesquioxane (HSQ) interlayer. HSQ is a flowable oxide with excellent thermal stability.