A preparation method for magnetic tunnel junctions with single crystal GaAs(001) barriers is demonstrated. The method is based on an epoxy bond and stop etch technique and does not require epitaxial growth of a semiconductor on top of a metal. Stable GaAs tunnel barriers down to 6 nm in thickness were prepared. The I–V measurements show a pronounced nonlinearity. Their variation with temperature depends strongly on the barrier thickness which is weak for the 6 nm barriers, a clear indication for quantum mechanical tunneling as the dominant transport channel.