High Resolution Deep Level Transient Spectroscopy of p-n diodes formed from p-type polycrystalline diamond on n-type silicon

High resolution Laplace Deep Level Transient Spectroscopy (LDLTS) at temperatures up to 450K has been applied to thin polycrystalline semiconducting diamond films deposited on n-type silicon. Such structures form p-n diodes and can be characterised by capacitance DLTS. The boron doped diamond films were grown by hot filament chemical vapour deposition and the diamond film thickness was 3-4 microns. The boron concentration in the diamond films ranged from 7x10(18) cm(-3) to 1x10(19) cm(-3). In the LDLTS an isothermal measurement of thousands of capacitance transients was made and then averaged, and the result was inverse transformed to find the trap emission rate. The temperature was chosen as the maximum of the conventional DLTS emission peak. Conventional DLTS showed a combination of majority and minority carrier emission from deep levels. Multiple peaks in the LDLTS spectra suggest that some of the defects are located in a strain field. Capture cross section measurements also show that these peaks exhibit a time dependent capture cross section, which is indicative of carriers being trapped at a large electrically active defect. It is shown in the paper that a combination of LDLTS and direct capture cross section measurements can be applied to semiconducting diamond and can be used to understand whether defects possess single or multiple energy levels, and whether the trapping is at an isolated point defect or in defects in the strain field of an extended defect.