Electronic transport through semiconductor barriers

Abstract

Electron transport across rectangular barriers, made of 200 A thick GaAlAs layers embedded in GaAs, and triangular barriers at the (n+)GaAs-(n)GalnP 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.

Defect-Enhanced Electron Transport through Semiconductor Barriers

“…The associated activation energy is the magnitude of the conduction band discontinuity, decreased by a factor proportional to the energy depth of the defect level involved. This decrease is indeed observed experimentally [6,7]. However, the experimental data are also strongly sensitive to the electric field [6], a fact that cannot be explained in terms of this mechanism.…”

“…This decrease is indeed observed experimentally [6,7]. However, the experimental data are also strongly sensitive to the electric field [6], a fact that cannot be explained in terms of this mechanism.…”

“…2b). The existence of this second mechanism has been experimentally proven in the case of GaAlAs/GaAs rectangular barriers 578 L. El Mir and J. C. Bourgoin and of GaInP/GaAs triangular barriers [6,13,15]. The defect responsible for it, in unintentionally doped as well as in n-type doped barriers, exhibits the characteristics of the defect usually labelled the DX center, a defect directly related to the residual or doping donor impurity [6,13].…”

“…However, when the magnitude of the current is measured, it is found to be large compared to the one expected from these mechanisms (see for instance [1 to 5]). Moreover, the temperature dependence of the current is such that an apparent lowering of the band offset is observed [6,7] and its value depends strongly on the applied electric field [6].…”

Thermionic emission perpendicular to bulk and multiquantum AlxGa1−xInP barriers

“…5 This classical thermionic approach has been successfully used in determining the conduction band offset present at Al x Ga 1−x InP/ GaInP junctions for various alloy compositions. 6 However, there are two areas of concern regarding this approach.…”