Deep levels in n-type high-purity material were studied by using optically detected deep-level transient spectroscopy. Optical injection, using light with an energy above the band-gap, resulted in the detection of centers in the minority half of the band-gap. Six deep minority carrier traps were detected in typical n-type high-purity material. These were found to be the same defects that had been found as majority carrier traps in p-type high-purity material. These deep defects were mainly Cu-related. A formula was derived which permitted the estimation of concentrations on the basis of optically detected deep-level transient spectra. It was shown that not only were the same defects present in n-type and p-type high-purity material, but their concentrations were also comparable.

A.Blondeel, P.Clauws, D.Vyncke: Journal of Applied Physics, 1997, 81[10], 6767-72