Doping and Temperature Dependence of Carrier Lifetime in 4H SiC Epitaxial Layers

Thick 4H-SiC epilayers have be grown with n-type and p-type doping in the range 1x10¹⁴ cm^‑3 to mid 1x10¹⁸ cm^‑3, with the purpose of investigating the influence of doping on carrier lifetime. Growth conditions were identical for all grown epilayers, except for the dopant gas flow rates. A drastic decrease in carrier lifetime was observed with increasing doping level, in both n-type and p-type layers. The decrease in lifetime could not be related to the Z_1/2 center but are rather due to an enhanced effect of direct band-to-band and Auger recombination’s (AR) at higher doping levels. Calculations of Auger coefficients for the recombination’s are indicating Auger recombination’s as the main recombination mechanism at the highest doping levels. Indications are made stronger from the temperature dependence of Auger coefficients. An increased background intensity arises around 400 K during temperature dependent time-resolved photoluminescence measurements of n-type epilayers are observed and are thought to be related to boron impurities.