GROWTH AND CHARACTERIZATION OF PHOSPHORUS-DOPED DIAMOND FILMS

Phosphorus-doped diamond films were grown from CH4 and H-2 using d.c. and microwave plasmas with PH3 as the dopant source. The P incorporati on which was quantified using secondary ion mass spectrometry varies b y more than two orders of magnitude for a given ratio of PH3 to CH4 in the gas phase. The lowest incorporation occurs in single-crystal (hom oepitaxial) layers and the highest occurs in the polycrystalline films with the smallest grain size, indicating that P incorporates preferen tially at grain boundaries. Conductivities of approximately 10(-10) to 10(-9) OMEGA-1 cm-1 were measured at room temperature for P-doped fil ms. Significant levels of Si and B impurities are unintentionally pres ent in these films, which may compensate any potential donor behavior of P. The homoepitaxial films were characterized by high resolution X- ray diffraction. The peak widths at half-maximum for the (004) reflect ion for all films are comparable with that of the bare IIa natural dia mond substrates (0.050-degrees), regardless of thickness or doping, su ggesting that the crystalline quality of the epitaxial layers is as go od or better than that of the substrates.