Conductive Si-doped α-(AlxGa1-x)2O3 thin films with the bandgaps up to 6.22 eV

This study systematically investigates the properties of (i) conductive Si-doped alpha-(AlxGa1-x)(2)O-3 thin films grown via a third generation mist chemical vapor deposition system and (ii) Schottky diodes (SDs) and metal semiconductor field-effect transistors (MESFETs) fabricated on them. The use of chloro(3-cyanopropyl)dimethylsilane as the Si dopant resulted in conductive thin films in a wide range of Al contents x from 0 to 0.3. The resistivity fluctuated in the range from 0.14 Omega cm to 0.35 Omega cm at x <= 0.05 and abruptly increased as x exceeded 0.05. Nevertheless, a resistivity of 1.2 k Omega cm was measurable in an (Al0.3Ga0.7)(2)O-3 film, whose bandgap of 6.22 eV was comparable to that of AlN. All the silver oxide SDs fabricated on these films functioned properly with the rectification ratios up to 10(5), while the MESFETs showed clear field-effect even in the alpha-(Al0.3Ga0.7)(2)O-3 film. Interestingly, a linear dependence of barrier heights on ideality factors was obtained in diodes formed between the source and gate electrodes of these transistors despite the differences in the bandgaps. This plot yielded the average or homogeneous barrier height of similar to 2.0 eV, suggesting that the Fermi level on the AgOy/Si:alpha-(AlxGa1-x)(2)O-3 interface was pinned at similar to E-c -2.0 eV regardless of the Al content x.