Electrical profiles in GaN/Al2O3 layers with conductive interface regions

Differential Hall-effect measurements are used to obtain profiles of the mo bility, 1, and carrier concentration, n, in a 6-1m-thick GaN layer grown on Al2O3 by hydride vapor phase epitaxy (HVPE). In the top 1-1m region (surfa ce), 1 1000 cm(2)/V-s and n 3 x 10(16) cm(-3), whereas in the bottom 0.75-i m region (interface), i 50 cm(2)/V-s and n 2 x 10(19) cm(-3). Throughout th e layer, the carrier concentration correlates well with the O and Si concen trations, with [Si] dominant near the surface, and [O] dominant near the in terface, proving the shallow-donor nature of O. The average mobility and ca rrier concentration in the top 5 1m, i.e., the "bulk" region, are close to the values deduced by a much simpler analysis, introduced previously.