Differential Hall-effect measurements are used to obtain profiles of the mobility, μ, and carrier concentration, n, in a 6-μm-thick GaN layer grown on Al2O3 by hydride vapor phase epitaxy (HVPE). In the top 1-μm region (surface), μ ≈ 1000 cm2/V-s and n ≈ 3 × 1016 cm−3, whereas in the bottom 0.75-μm region (interface), μ ≈ 50 cm2/V-s and n ≈ 2 × 1019 cm−3. Throughout the layer, the carrier concentration correlates well with the O and Si concentrations, with [Si] dominant near the surface, and [O] dominant near the interface, proving the shallow-donor nature of O. The average mobility and carrier concentration in the top 5 μm, i.e., the “bulk” region, are close to the values deduced by a much simpler analysis, introduced previously.
