High-Power Vertical-Junction Field-Effect Transistors Fabricated on Low-Dislocation-Density GaN by Epitaxial Lift-Off

"In this program, we will develop a breakthrough technology that will enable wafer-scale epitaxial lift-off (ELO) of GaN power device heterostructures from low-dislocation-density bulk GaN substrates. This technology will be used to provide a low-cost vertical junction field effect transistors (VJFETs) with high breakdown voltage (greater than 1,200 V) and high current capability (greater than 100 A). Despite the recent commercial success of GaN-based optical and electronic devices, the high dislocation density resulting from the use of mismatched substrates leads to fundamental performance, reliability, and thermal conductivity limitations in vertical power device applications. Bulk GaN substrates with low dislocation density (less than 10^5 cm-2) are under development in small diameters (1 inch - 2 inch) but at high cost. MicroLink is an industry leader in the commercialization of ELO and in the reuse of GaAs and InP substrates for multi-junction solar cells. MicroLink is also a leading producer of GaAs VJFETs and HBTs. The proposed principal investigator carried out pioneering work on photoelectrochemical wet etching of GaN materials. We will leverage this expertise to develop a new ELO-based layer transfer technology using reusable bulk GaN templates for epitaxial growth to enable high quality GaN materials at dramatically lower cost. We will demonstrate the viability of this technology using a novel vertical junction FET device, which leverages our experience in producing GaAs VJFETs. We have assembled a team of world-class partners with expertise on GaN epitaxial growth, bulk GaN substrates, modeling, power device design, and device testing. "