Millikelvin magnetotransport studies are carried out on heavily $n$-doped wurtzite GaN:Si films grown on semi-insulating GaN:Mn buffer layers by metal-organic vapor phase epitaxy. The dependence of the conductivity on magnetic field and temperature is interpreted in terms of theories that take into account disorder-induced quantum interference of one-electron and many-electron self-crossing trajectories. The Rashba parameter ${\alpha }_{\text{R}}=(4.5\pm 1)$ meV Å is determined, and it is shown that in the previous studies of electrons adjacent to GaN/(Al,Ga)N interfaces, bulk inversion asymmetry was dominant over structural inversion asymmetry. The comparison of experimental and theoretical values of ${\alpha }_{\text{R}}$ across a series of wurtzite semiconductors is presented as a test of current relativistic ab initio computation schemes. Low-temperature decoherence is discussed in terms of disorder-modified electron-electron scattering.

• Received 5 March 2014
• Revised 18 April 2014

DOI:https://doi.org/10.1103/PhysRevB.89.205201