Deep Levels in n-Type 4H-Silicon Carbide Epitaxial Layers Investigated by Deep-Level Transient Spectroscopy and Isochronal Annealing Studies

Deep levels were investigated by the capacitance mode deep-level transient spectroscopy (C-DLTS) on 4H-SiC Schottky barrier diodes fabricated on
$50\;\mu\text{m}$
-thick n-type 4H-SiC epitaxial layers. C-DLTS scans from 80 K to 800 K revealed the presence of Ti(c),
${{\rm Z}_{1/2}}$
,
${\rm EH}_{5}$
, and
${\rm EH}_{6/7}$
defect levels in the energy range from 0.17 to 1.6 eV below the conduction band edge. The annealing out of primary defects and generation of secondary defects were investigated by systematic and thorough C-DLTS studies from prior and subsequent isochronal annealing in the temperature range from 100 °C to 800 °C. The capture cross-section of Ti(c) was observed to decrease up to 400 °C and remained unchanged at higher annealing temperatures. Defect densities were shown to decrease up to 200 °C and gradually increase at higher temperatures. The
${{\rm Z}_{1/2}}$
and
${\rm EH}_{6/7}$
defect parameters showed similar variation for the temperature range studied. The thermal evolutions of these deep levels in n-type 4H-SiC epitaxial layers are analyzed and discussed for the first time.