In this study, silicon doping using flow rate modulation epitaxy was found to produce better characteristics compared with conventional metal-organic chemical vapor deposition of the same growth system. The amount of phosphine is very critical in this new growth method. A lower compensation ratio (0.1) and higher mobility (3200 cm(2) V-1 s(-1) at 300 K) are obtained under the optimum conditions. These are very important for application to high speed and low noise devices.