Homoepitaxial diamond growth by high-power microwave-plasma chemical vapor deposition

Abstract

We have investigated homoepitaxial diamond growth by high-power microwave-plasma chemical-vapor-deposition (MPCVD) method. The diamond growth rate R g increased linearly with increase in the methane flow-rate ratio in the total source gas flow, C me , only for C me > 4 % while increasing non-linearly with the C me for C me < 4.0 % under the high microwave power condition of 3.8 kW. In the case of the present high-power MPCVD, saturation of R g, that often occurred at C me ≈ 1.0 % in conventional MPCVD cases, was not observed in the whole C me range examined (⩽32%). The crystalline quality of diamond films became relatively better and the surface morphology became smooth without non-epitaxial crystallites in the C me range from 4.0 to 8.0% under the growth conditions. For R g > 10 μm/h, however, formation of round-shape hillocks, various defects and vacancies including nitrogen-related CL centers occurred in some cases. It is found that these degradations, which occurred for C me > 10.0 % in the present MPCVD case, can be suppressed by increasing plasma density using higher microwave power of 4.7 kW and higher total gas pressure of 160 Torr. Possible reasons for the observed advantages in the present high-power MPCVD method are discussed.