Heavy phosphorus doping by epitaxial growth on the (111) diamond surface

Semiconducting n-type diamond can be fabricated using phosphorus as a substitutional donor dopant. The dopant activation energy level at 0.58 eV is deep. At high dopant concentrations of 10(20) cm(-3) the activation energy reduces to less than 0.05 eV. Phosphorus doping at concentrations of 10(20) cm(-3) or higher has been achieved with epitaxial growth on the (111) diamond crystallographic surface. In this work epitaxial growth of diamond with high phosphorus concentrations exceeding 10(20) cm(-3) is performed using a microwave plasma-assisted chemical vapor deposition process with process conditions that include a pressure of 160 Torr. This pressure is higher than previous phosphorus doping reports of (111) surface diamond growth. The other growth conditions include a feedgas mixture of 0.25% methane and 500 ppm phosphine in hydrogen, and a substrate temperature of 950-1000 degrees C. The measured growth rate was 1.25 mu m/h. The room temperature resistivity of the heavily phosphorus doped diamond was 120-150 ohm-cm and the activation energy was 0.027 eV.