Acceptor compensation by dislocations related defects in boron doped homoepitaxial diamond films from cathodoluminescence and Schottky diodes current voltage characteristics

This document shows that new electrically active defects can develop in the homoepitaxial layer grown on Ib diamond substrates, related to the increase of the dislocation density. Deep centres, which are able to compensate the boron acceptors, specially when the growth process allows boron incorporation below 10(15) cm(-3) like achieved in the samples, are identified after heating in an inert gas ambient both from photoinduced current transient spectroscopy (PICTS) and changes in Schottky diode current-voltage characteristics. Cathodoluminescence spectra are used to monitor the bands and excitonic lines, some of them being specific of dislocations. A correlation is demonstrated between the onset of properties characteristic of a compensated semiconductor and the increase of signals associated to dislocations in cathodoluminescence spectra. These modifications are thermally driven only when the samples are laid on a heating holder immerged in an inert gas, suggesting that a temperature gradient induced an additional stress which finally led to plastic relaxation of the tensile strain in the homoepitaxial layer by an increase of the dislocation density. New deep centres being simultaneously created in this degradation process, the problem of overcoming the onset of these defects for implementing high voltage devices is discussed. (c) 2006 WREY-VCH Verlag GmbH & Co. KGaA, Weinheim.