Double correlation technique (DDLTS) for the analysis of deep level profiles in semiconductors

Abstract

A very sensitive technique is presented which can be applied to determine deep level profiles in space-charge layers of Schottky barriers orpn-junctions. The method uses an extended transient capacitance technique with correlation similar to Lang's DLTS technique. The extension of DLTS to double correlation DDLTS is necessary to resolve the deep level profile and to exclude the field dependence of the capture cross-section and contact effects. By using a double-pulse capacitance transient and correlation, these undesired effects can be subtracted. Profiles can be determined for deep levels at concentrations 10⁴ times lower than the background doping. Results are reported for epitaxial GaAs which showed one major deep level at 0.18 eV below the conduction band. Near the interface to the substrate, a slight shift in energy from 0.18 to 0.19 eV is observed. A second level at 0.43 eV decays into the epi-layer in the form of a diffusion tail.