Characterization of phosphorus-doped homoepitaxial (1 0 0) diamond films grown using high-power-density MWPCVD method with a conventional quartz-tube chamber

Phosphorus-doped n-type homoepitaxial diamond films have been successfully grown at high substrate temperatures (>1000 °C) on high-pressure/high-temperature-synthesized type-Ib single-crystalline diamond (1 0 0) substrates, by using a conventional microwave plasma chemical-vapor-deposition (CVD) system with high power densities. The deposition system employed in this work had an easily exchangeable 36 mm inner-diameter quartz-tube growth chamber. The homoepitaxial diamond films thus grown were characterized by means of Hall-effect measurements with an AC magnetic field, atomic force microscope observations and secondary ion mass spectrometry techniques. The dependences of the substrate temperature (≤1300 °C) and the P/C ratio in the source gas (≤9900 ppm) on the specimen features were investigated. The optimum substrate temperature deduced was ≈1160 °C, which was also applicable to the CVD growth of undoped homoepitaxial diamond layers. The n-type conductions with an activation energy ≈0.6 eV were observed for the specimens with amounts of the P atoms incorporated to ≈1.5 × 10¹⁸ cm⁻³ whereas the doping efficiencies changed from ≈0.06% to ≈0.92% with the growth condition. Possible origins for these results are discussed in relation to the growth mechanism.