Electrical properties of thick boron and nitrogen contained CVD diamond films

The acceptor and donor defects of thick (approx. 0.4 mm) free-standing boro n and nitrogen containing microwave plasma CVD polycrystalline diamond film s were investigated. Charge-based deep level transient spectroscopy (Q-DLTS ) was applied to study impurity-induced defects, their density and energy d istribution in the energy range of 0.01 eV less than or equal to E - E-v le ss than or equal to 1.1 eV above the valence band. It was shown, that diffe rential capacitance-voltage, and Hall effect measurements combined with DLT S data can be used to determine the degree of compensation, and the concent ration of compensating donors (mostly the positively charged single-substit utional nitrogen (N+)) in p-type CVD polycrystalline diamond films. It was found, that incorporated boron atoms induce three levels of electrically ac tive defects. Two of them with concentration (2-3) x 10(16) cm(-3) each hav e 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 gene ral caterer of holes in low-doped films. The total concentration of electri cally active uncompensated accepters in all p-type diamond samples was appr oximately 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 ro om temperature. If assumed that compensating donors are mostly nitrogen, th e films contained no less than 3 x 10(16) cm(-3) of N+. (C) 2001 Elsevier S cience B.V. All rights reserved.