Interface and bulk defects in SiC/GaN heterostructures characterized using thermal admittance spectroscopy

SiC/GaN p-n and n-n heterostructures grown by low pressure chemical vapor deposition were investigated using thermal admittance spectroscopy. Different kinds of defects were isolated and located. Evidence of a distribution of defects at the p-SiC/n-GaN interface is given as having thermal activation energies of (87+/-3) meV at 5 V and (72+/-4) meV at 8 V bias. Additionally, three bulk defects with activation energies between 155 and 175 meV were found. By comparison with admittance spectra of the p-type SiC substrate, one level was identified as Al acceptor in SiC, whereas the other defects are electron traps in the GaN layer. (C) 1999 American Institute of Physics. [S0003-6951(99)00110-2].