Electrical properties of heavily Sn-doped (AlGa)2O3 layers on β-Ga2O3 (010) substrates

We report on the critical layer thickness for (AlGa)(2)O-3 hetero-epitaxial growth on beta-Ga2O3 (010) substrates via plasma-assisted molecular-beam epitaxy and on the electrical properties of heavily tin-doped (AlGa)(2)O-3 layers. The aluminum composition in the (AlGa)(2)O-3 layers was reproducibly controlled within 19% by changing aluminum fluxes. We achieved the pseudomorphic growth of the 1050 nm thick (Al0.12Ga0.88)(2)O-3 and 420 nm thick (Al0.15Ga0.85)(2)O-3 layers on beta-Ga2O3 (010) substrates. The electron concentration, contact resistivity, and sheet resistance of the (Al0.10Ga0.90)(2)O-3 layer with a tin concentration of 4 x 10(19) cm(-3) were 1 x 10(18) cm(-3), 3 x 10(-5) omega cm(2), and 9 x 10(2) omega/rectangle, respectively.