Effects of localized boron states on the transport properties of n-BGaInAs

The incorporation of isovalent boron on cation sites of GaAs results in strongly localized electronic states resonant with the conduction band. All present experimental and theoretical results indicate that these states have only minor influence on the conduction band structure. We show however that such states strongly affect the electronic transport behaviour of this unusual semiconductor alloy. We study the influence of these boron cluster states on the electronic transport of n-type BGaInAs-layers. We performed magnetotransport measurements at temperatures from 1.6 K to 300 K using magnetic fields up to 10 T and hydrostatic pressure up to 20 kbar. At ambient pressure and low carrier concentration both strong negative MR effects at low fields and a giant exponential positive MR at high magnetic fields can be observed. The latter is regarded as proof of a hopping transport mechanism and is interpreted as a metal insulator transition under the influence of an external magnetic field. Under hydrostatic pressure the results are dominated by the complex interplay between extended band states, localized boron states and dopant states