Electrical properties of thick boron and nitrogen contained CVD diamond films

The acceptor and donor defects of thick (approx. 0.4 mm) free-standing boron and nitrogen containing microwave plasma CVD polycrystalline diamond films were investigated. Charge-based deep level transient spectroscopy (Q-DLTS) was applied to study impurity-induced defects, their density and energy distribution in the energy range of 0.01 eV less than or equal to E - E-v less than or equal to 1.1 eV above the valence band. It was shown, that differential capacitance-voltage, and Hall effect measurements combined with DLTS data can be used to determine the degree of compensation, and the concentration of compensating donors (mostly the positively charged single-substitutional nitrogen (N+)) in p-type CVD polycrystalline diamond films. It was found, that incorporated boron atoms induce three levels of electrically active defects. Two of them with concentration (2-3) x 10(16) cm(-3) each have activation energies of 0.36 and 0.25 eV with capture cross-sections of 1.3 x 10(-13) and 4.5 x 10(-19) cm(2), respectively. The third type of defect has an activation energy of 0.02 eV, capture cross-section 3 x 10(-20) cm(2) and concentration 10(15) cm(-3), this shallow trap being a probable general caterer of holes in low-doped films. The total concentration of electrically active uncompensated accepters in all p-type diamond samples was approximately 2 x 10(17) cm(-3) with hole concentration of approximately 1.5 x 10(14) cm(-3) and hole mobility in the range of 30-40 cm(2) V-1 s(-1) at room temperature. If assumed that compensating donors are mostly nitrogen, the films contained no less than 3 x 10(16) cm(-3) of N+. (C) 2001 Elsevier Science B.V. All rights reserved.