Electrical characterisation of defects in polycrystalline B-doped diamond films

Admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS) have been applied to B-doped thin polycrystalline diamond films deposited on p(+)-silicon by hot filament chemical vapour deposition. Films with two boron concentrations (1.5x10(19) cm(-3) and 4x10(19) cm(-3)) were selected to study the effect of B concentration on the electronic states in CVD-diamond. We have investigated whether these deep states arise from point or extended defects. DLTS and AS find two hole traps, E1 (0.29 +/- 0.03 eV) and E2 (0.53 +/- 0.07 eV), in both films. A third level, E3 (0.36 +/- 0.02 eV) was also detected in the more highly doped film. The defect levels E1 and E2 exhibited behaviour typical of extended defects, which we suggest may be due to B segregated to the grain boundaries. In contrast, the defect level E3 exhibited behaviour characteristic of an isolated point defect, which we attribute to B-related centres in bulk diamond.