Electrically active defects in boron doped diamond homoepitaxial layers studied from deep level transient spectroscopies and other techniques

Homoepitaxial thin films of boron doped diamond are investigated with the help of Fourier transform deep level transient spectroscopy (FT-DLTS) and high resolution isothermal transient spectroscopy (HR-ITS) in order to determine the properties of hole traps. Conductivity studies and other characterisation techniques of defects are also used to bring complementary information. The main conclusions are as follows: (i) many hole traps can be found with activation energies in the range 0.9-1.6 eV; (ii) most of them show inwards decreasing concentrations, which passes below 10 15 /cm 3 at a depth close to a few hundred nanometers from the surface; (iii) some of them are metastable, in the sense the emission rate distribution undergoes changes after thermal treatments performed at temperatures well below those used for growth and previous annealing. These two last facts suggest that hydrogen atoms may be involved in charged defects. In other samples, an irreversible decrease of the conductivity correlated with the increase of the cathodoluminescence (CL) A band demonstrates that a deep donor is connected with dislocations and acts as a very efficient compensating centre in the first 400 nm just below the surface but with a decreasing concentration deeper inside the homoepitaxial layer. The physical origin of these deep levels is discussed and believed to be likely connected with hydrogen atoms.