Epitaxial growth and electric properties of γ-Al2O3(110) films on β-Ga2O3(010) substrates

Epitaxial growth and electrical properties of gamma-Al2O3 films on beta-Ga2O3(010) substrates were investigated regarding the prospect of a gate oxide in a beta-Ga2O3-based MOSFET. The gamma-Al2O3 films grew along the [110] direction and inherited the oxygen sublattice from beta-Ga2O3 resulting in the unique in-plane epitaxial relationship of gamma-Al2O3 [110] parallel to beta-Ga2O3[001]. We found that the gamma-Al2O3 layer had a band gap of 7.0 eV and a type-I band alignment with beta-Ga2O3 with conduction- and valence-band offsets of 1.9 and 0.5 eV, respectively. A relatively high trap density (congruent to 2 x 10(12) cm(-2) eV(-1)) was found from the voltage shift of photoassisted capacitance-voltage curves measured for a Au/gamma-Al2O3/beta-Ga2O3 MOS capacitor. These results indicate good structural and electric properties and some limitations hindering the better understanding of the role of the gate dielectrics (a gamma-Al2O3 interface layer naturally crystallized from amorphous Al2O3) in the beta-Ga2O3 MOSFET. (C) 2016 The Japan Society of Applied Physics