QSS-μPCD measurement of lifetime in silicon wafers: advantages and new applications

AbstractWe present a version of microwave photoconductance decay, μPCD, measurement of lifetime in silicon photovoltaics which enables simultaneous determination of the carrier decay lifetime, τeff, and injection level, Δn, with the capability of scanning over a broad range of steady state generation including 1 sun. The present μPCD version, referred to as QSS-μPCD, is a refined bias light PCD. It combines scanning of near steady-state generation, G, and pulsed laser μPCD parameter free determination of !!“”, for any given G. By reversing the quasi-steady-state photoconductance QSSPC procedure the injection level is determined as Δn=Gτeff. This is achieved for the first time without a requirement for absolute photoconductance calibration or the requirement for carrier mobility values. Moreover, the approach enables tuning measurement to optimize conditions for achieving exponential transients and for elimination of the interference from trapping and space charge conductance modulation. The unique advantage of simultaneous determination of τeff, and Δn permits the use of the Kane and Swanson method for measurement of the emitter saturation current, J0. Using spatially resolved μPCD capability, mapping of J0 is demonstrated