Deep Level Transient Spectroscopy on Silicon of Lower Purity^*

V. Schlosser, K. Wendl

• Ludwig Boltzmann Institut für Festkörperphysik, Wien

• Institut für Festkörperphysik University of Vienna

• A-1060 Wien, Kopernikusgasse 15 (AUSTRIA)

ABSTRACT. Different samples of crystalline silicon prepared from metallurgical meltstock have been annealed at temperatures between 600 degrees Centigrade and 1020 degrees Centigrade. All samples are p-silicon -resistivity 0.03 Ohm.cm to 0.3 Ohm.cm-. MIS structures and mesa diodes etched from planar pn-junctions were examined with capacitive deep level transient spectroscopy (DLTS). In all our samples hole traps correlated with iron have been identified. Concentration and distribution of energy levels depend very strongly on the annealing temperature. A correlation between the surface concentration of interstitial iron and an energy level situated at E_v+E_t=0.32eV has been observed. For all samples the minority carrier diffusion length is limited by this point defect once the concentration exceeds 1x10¹⁴ cm^-3. From our results we conclude that the most harmful residual impurity in our samples is iron.

^*)work supported by the Fonds zur Forderung Wissenschaftlicher Forschung.