Impact of surface preparation on the epitaxial growth of SrTiO3 on ScAlN/GaN heterostructures

Heterogeneous integration of functional oxides with ultra-wide bandgap (UWBG) semiconductors is desired for the realization novel hybrid systems applicable to a wide array commercial electronics and defense applications. In this work, we demonstrate growth crystalline SrTiO3 (STO) thin films on high-electron-mobility transistor (HEMT) heterostructures based an emergent UWBG semiconductor ScAlN, used as barrier layer GaN channel, determine effects pre-growth chemical treatments ScAlN surface resultant heterostructure properties. We investigate wet cleans solvents, piranha solution, UV ozone hydrofluoric acid, sulfuric-phosphoric acid mix prior STO growth, show that commonly solution degrades surface, thereby reducing crystal quality deposited layers lowering channel mobility. among studied, solvent were least disruptive electrical properties evidenced from Hall effect measurements, but clean results in best oxide crystallinity, determined structural characterizations. perform transmission electron microscopy imaging piranha-treated sulfuric-phosphoric-treated samples compare microstructure find while intermixing occurs at oxide-nitride interfaces both samples, interface roughness lower grain size larger sample treatment. This work demonstrates first epitaxial motivates STO/ScAlN/GaN material platforms high-frequency, high-power-density HEMTs.