The invention provides a single-step method for removing bulk metal contamination from III-V semiconductor substrates. The method comprises immersing a metal contaminated III-V semiconductor substrate in a mixture of sulfuric acid and peroxide with a volume ratio of sulfuric acid to peroxide (e.g., hydrogen peroxide) between about 3:1 and about 9:1. After treating the III-V semiconductor substrates with the sulfuric acid-peroxide mixture, the bulk metal contamination may be substantially removed from the substrate while a surface roughness of the substrate after treatment of below about 0.5 nm RMS (2 μm×2 μm) is obtained. The invention further provides a method for manufacturing a semiconductor device by removing bulk metal contamination according to the single-step method of the invention before performing processing steps for forming the semiconductor device.