Lifetime spectroscopy for defect characterization: Systematic analysis of the possibilities and restrictions

Abstract

Carrier lifetime is very sensitive to electrically active defects. Apart from detecting the presence of recombination active defects, lifetime measurements allow for a direct identification of defects if the temperature and injection dependence of carrier lifetime is analyzed. In the present work, the Shockley–Read–Hall (SRH) equation is analyzed from a theoretical point of view in order to demonstrate the possibilities and basic restrictions of i_njection- and t_emperature-d_ependent l_ifetime s_pectroscopy (IDLS and TDLS), respectively. To show the variety of attainable curve shapes and to evaluate their suitability for a spectroscopic determination of defect parameters, the general impact of the defect and material parameters on the injection and temperature dependence of SRH lifetime is investigated systematically. From this the basic requirements for an unambiguous defect characterization are derived. The experimental applicability of lifetime spectroscopy is demonstrated by TDLS and IDLS measurements performed on an intentionally molybdenum contaminated Si sample using the microwave-detected photoconductance decay technique and the quasi-steady-state photoconductance technique, respectively. The energy level of 0.335 eV below the conduction band determined from TDLS corresponds well with deep level transient spectroscopy-values reported in literature and could also be determined from the corresponding IDLS curve though not unambiguously.