Minority carrier diffusion length measurements in 6H-SiC

Minority carrier diffusion lengths were measured as a function of temperature and position along the growth axis of lightly nitrogen doped boules of 6H-SiC grown by the physical vapor transport technique. It is shown that the diffusion lengths increase from 1 to 2 microns in the seed portion of the boule to about 4 microns in the tail portion of the boules. Deep levels transient spectroscopy measurements revealed the presence of deep electron traps with the activation energies of 0.35 eV , 0.5 eV , 0.65 eV , and 1 eV . The densities of all these traps decrease when moving from seed to tail of the boules. A good correlation between the change of the lifetime values and the density of the 0.65 eV and 1 eV electron traps was observed. The measured lifetimes show an increase with temperature following a power law that suggests that the hole capture could be determined by cascade capture process.