Characteristics of Single Crystalline Rutile GeO2 Film Grown on Sapphire by Chemical Vapor Deposition with a high growth rate ∼2.2 μm/hr

Abstract

Rutile GeO2 with ultra-wide energy bandgap (UWBG) similar to 4.68 eV and theoretically ambipolar dopability has high potential as a next generation UWBG semiconductor. However, the growth of the material with either good crystal quality, high growth rate, or at a low cost has not yet been achieved at a satisfying level. We report the system design of the low-pressure chemical vapor deposition (LPCVD) growth of rutile GeO2. High purity Ge granules and GeO2 powder were used as Ge source to generate GeO precursor in the system. The r-GeO2 film was grown on an a-sapphire substrate to enable cheap and large-scale r-GeO2 production. The growth rate as high as 2.2 mu m/hr was achieved. X-ray diffraction (XRD) analysis revealed single crystalline (101) r-GeO2 film with peak intensity comparable to sapphire substrate. On- and off-axis XRD rocking curve scans showed full-with at half maximum in the range of 511-806 arcsec indicating both edge and screw dislocation density at low 10(9) cm(-2). Transmission electron microscopy (TEM) measurements indicated dislocations emerging from r-GeO2 / sapphire interface, which reduces with thickness, developing high-quality crystallinity. Atomic resolution TEM analysis unveiled the nature of highly ordered ultra-sharp r-GeO2 / sapphire interface. This study paves the way for the realization of the promising r-GeO2 to meet various growth-related requirements using a scalable custom designed LPCVD system.