Compensation effects at electron traps in semiconductors

Artikel i vetenskaplig tidskrift, 2013

The basic qualities for fulfilling the Meyer-Neldel rule (MNR) for thermal electron emission from semiconductor traps are investigated. A trap model including vibronic properties is used with varying entropy arising from the change in elasticity of the ionic part of the trap potential when an electron transition takes place. This gives rise to a system where the compensation effect originates from the increasing entropy change as a function of the enthalpy supply needed for the transition process in concord with Yelon-Movaghar theory. The entropy increase connects to a decrease in the activation energy for electron capture, which amplifies the compensation effect for MNR manifestation. By comparing with experimental data, the result achieved from the model clarifies the experimental observation of class partitioning for centers in GaAs, obeying the MNR. Furthermore, it is demonstrated that traps at metal-oxide-silicon interfaces, with the same properties as bulk traps following the MNR, give rise to capture cross-sections steeply increasing with the Gibbs free energy involved in carrier emission, as found by experiment.