Electronic transport through semiconductor barriers

Electron transport across rectangular barriers, made of 200 AA thick GaAlAs layers embedded in GaAs, and triangular barriers at the (n+)GaAs-(n)GaInP interface has been studied. Current versus voltage and temperature characteristics have been analysed in order to extract the different mechanisms that induce this transport, and to determine the temperature and electric field range in which they apply. At low temperature and high field the current is driven by the Fowler-Nordheim regime. At higher temperatures the current is dominated by a defect-induced mechanism. This mechanism consists of the thermal emission of electrons into the barrier conduction band from defects lying in the barrier that can be refilled by tunnelling. The defect involved appears to be the deep state associated with the donor impurity, i.e. the DX centre. This study demonstrates that the apparent band offset depends strongly on the experimental conditions under which it is measured.