Characterization of conduction in LTG-GaAs

The d.c. and a.c. electrical conduction has been studied in GaAs layer grown by molecular beam epitaxy between 150°C and 400°C. It is found that the admittance versus frequency, Y(ω), exhibits a universal behaviour. At low frequencies Y(ω) is constant, then exhibits a minimum at ω_m. At high frequencies Y(ω) varies linearly as ω showing that conduction occurs via hopping. The temperature dependence of Y(0) indicates that this hopping conduction occurs in a partially filled band related to EL2 defects, the direct relationship between ω_m and Y(0) demonstrates the existence of a percolation regime, i.e. of a conduction limited by insulating regions which we attribute to space charge regions developed around as precipitates