The influence of the Hall scattering factor on the determination of activation energies of the nitrogen donors in 4H-SiC epitaxial layers

Abstract

In 4H-SiC, the most common donor impurity, nitrogen, is not always completely ionized at room temperature, so its activation energy can have a direct impact on device characteristics. Values of the activation energies of the nitrogen donors in SiC as determined by Hall effect measurements are frequently higher than values determined by optical measurements which should give a maximum value. The Hall scattering factor r/sub H/ can skew activation energies if one uses the common approximation r/sub H/=1, so an investigation of this quantity was undertaken. r/sub H/ can be measured if magnetic fields larger an 1//spl mu//sub D/ are available where /spl mu//sub D/ is the electron drift mobility. The Hall scattering factor was measured on four 4H-SiC epitaxial layers at the National High Field Magnet Lab (NHMFL) in Tallahassee, Florida, USA with magnetic fields of up to 30 T. Nitrogen donor activation energies extracted from carrier concentration data corrected with Hall scattering factor information are within experimental error equal to these. The correction is not significant and cannot account for the experimental difference between electrical and optical data. Details of the procedure for extracting activation energies are presented.