Influence and mutual interaction of process parameters on the Z1/2 defect concentration during epitaxy of 4H-SiC

The development of bipolar 4H-SiC devices for high blocking voltages requires the growth of high carrier lifetime epitaxial layers with low Z1/2 concentrations. This paper shows a comprehensive investigation of the influence of epitaxial growth parameters (C/Si ratio and growth temperature) on Z1/2 concentration and minority carrier lifetime. On the basis of a discovered exponential correlation of Z1/2 with the C/Si ratio and growth temperature, a competitive low Z1/2 concentration of 1.9∙1012 cm-3 could be achieved by lowering the growth temperature and switching to higher C/Si ratio. Thermodynamic considerations by an Arrhenius approach reveal a dependency of the formation enthalpy of Z1/2 on the thermal process and process conditions of the epitaxial growth. Furthermore, the correlation between Z1/2 and the effective minority carrier lifetime confirms the occurrence of a necessary second recombination mechanism beside the common recombination at deep levels by Shockley-Read-Hall for low Z1/2 concentration.