Growth of GaN on lithium gallate substrates for development of a GaN thin compliant substrate

Since we have found that an entire substrate can be chemically removed in less than 5 min and since GaN is impervious to chemical etching, the GaN on lithium gallate (LGO) system is an excellent template (due to near infinite etch selectivity) for developing a thin film/compliant GaN substrate. Here we report on our efforts to grow GaN on LGO, including improvement of the atomic surface morphology using pregrowth pretreatments. We also report the first transferred thin film GaN substrate grown on LGO, transferred off of LGO and mounted on GaAs. With this approach, (InAl)GaN alloys can be grown on thin GaN films, implementing a "compliant" substrate for the nitride alloy system. In addition, the flexibility of bonding to low cost Si, metal or standard ceramic IC packages is an attractive alternative to SiC and hydride vapor phase epitaxy GaN substrates for optimizing cost verses thermal conductivity concerns. We have demonstrated high quality growth of GaN on LGO. X-ray rocking curves of 145 arcsec are shown on a 0.28 μm thick films. For the first time, we present data on the out-of-plane crystalline quality of GaN/LGO material. Likewise, we show two orders of magnitude improvement in residual doping concentration and factors of 4 improvement in electron mobility. We show substantial vendor to vendor and intravendor LGO material quality variations. We have quantified the desorption of Ga and Li from the surface of LGO at typical growth temperatures using in situ desorption mass spectroscopy and x-ray photoelectron spectroscopy.