Growth and Characterization of Phosphorus Doped n-Type Diamond Thin Films

Phosphorus (P) doped diamond thin films were grown by microwave plasma-assisted chemical vapor deposition (CVD) using phosphine (PH3) as a dopant source. The addition of PH3 in the gas ambient significantly influenced the optimal growth condition for diamond. The {111} surface of diamond was found to be the best surface as substrate for the growth of P-doped diamond. At a methane to hydrogen ratio of 0.15% and a substrate temperature of 950 °C, smooth {111} oriented homoepitaxial diamond thin films are obtained even with the addition of PH3 up to 1000 ppm to CH4. The epitaxial films grown with PH3/CH4 = 600 to 20000 ppm have shown clear n-type conduction as confirmed by Hall effect measurements over a wide temperature range. The activation energy of electrons was about 0.55 eV deduced from the temperature dependence of the carrier concentration. For the lightly doped sample, the Hall mobility of 28 cm2/Vs has been obtained in a temperature range of about 370 to 700 K.