High intensity magnetic fields for the identification and study of donors in epitaxial gallium arsenide

High intensity magnetic fields are needed for the far infrared photoconductivity method to be used reliably in the identification of unitentional contaminants in ultra high purity epitaxial GaAs. We show experimental evidence that the inhomogeneous Stark broadening of the 1s→2p (m=?1) transition of the hydrogen-like donor almost disappears as the magnetic field is increased to 20 Tesla. Since the spectral lines also become narrower and the central cell correction (chemical shift) becomes larger, the “signature curve” method of identification permits positive identification of donor species. In particular, the donors Ge and Se have been identified in specimens that were reported to contain carbon and Sn respectively.