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/spl deg/C and 400/spl deg/C. It is found that the admittance versus frequency, Y(/spl omega/), exhibits a universal behaviour. At low frequencies Y(/spl omega/) is constant, then exhibits a minimum at /spl omega//sub m/. At high frequencies Y(/spl omega/) varies linearly as /spl omega/ 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 /spl omega//sub 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.