The 1/f noise in n-GaAs epitaxial layers grown by molecular beam epitaxy was investigated at room temperature for various doping concentrations. The measured 1/f noise is a bulk effect. The noise parameter a between 10-4 and 10-3 was found to be dependent on the doping concentration.
Ren, L., & Leijs, M. R. (1991). 1/f noise at room temperature in n-type gallium arsenide grown by molecular beam epitaxy. Physica B: Condensed Matter, 172(3), 319-323. https://doi.org/10.1016/0921-4526(91)90449-O