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

Abstract

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 °C. The measured growth rate was 1.25 μm/h. The room temperature resistivity of the heavily phosphorus doped diamond was 120–150 Ω-cm and the activation energy was 0.027 eV. • Epitaxial growth of n-type diamond on the (111) surface witha phosphorus concentration exceeding 10 20 cm –3 . • Plasma CVD n + doped diamond growth is done at a deposition pressure of 160 Torrwith agrowth rate of 1.25 μm/hr. • The n + doped diamond has a room temperature resistivity of150 Ω-cm.