| Deep-level transient spectroscopy (DLTS) has characterized most deep-level impurities in semiconductors. It was originally based on detection of time-dependent junction capacitance due to carrier emission from bulk deep traps as a function to temperature. Semi-insulating (SI) GaAs, however, causes several measurement problems which are mainly due to a very low free carrier density and a higher concentration of a compensating deep-level impurity than those of shallow-level impurities. Surface photovoltage and microwave reflectance measurements have been used to overcome these limitations, and they offer noncontact DLTS variants. Both techniques use optical excitation to generate excess carriers.;In this thesis, we introduce photothermal radiometric deep-level transient spectroscopy (PTR-DLTS). It does not require any electrical contact to probe the excess carriers since it detects time-dependent emissivity of blackbody radiation from a semiconductor that responds to a square wave, above bandgap light pulse. PTR-DLTS simplifies the noncontact DLTS apparatus by eliminating any probe beam or electrical probe requirements. Furthermore, PTR-DLTS promises a high spatial resolution which is limited by the excitation beam spot size. (Abstract shortened by UMI.). |
