Electrical scattering mechanism evolution in un-doped and halogen-doped BiOSe single crystals.

Recently the layered oxide semiconductor BiOSe was hotly explored for its ultrahigh mobility and ultrafast photo-response whose physical origins need to be further explored or elucidated. Here, we have grown halogen (Cl, Br, I) doped and un-doped BiOSe single crystals by a melt-solidification method. Comparative electrical transport characterizations and detailed data-analysis substantiate that the electron-electron scattering is the major source of resistivity in un-doped BiOSe crystals; however, in halogen-doped BiOSe crystals, electron-electron scattering is only effective at low temperature (<60 K) and subsequently electron-phonon-interaction scattering is dominated to resistivity. Hall measurement and analysis show that electron concentration of halogen-doped BiOSe (∼10cm) is one-order higher than un-doped one (∼10cm), but the carrier mobility of halogen-doped BiOSe at 2 K (∼10cmVs) is reduced by more than two orders than un-doped ones (∼10cmVs). Three kinds of relaxation time (due to the impurity scattering, electron-electron scattering and electron-phonon scattering), calculated by linear-response theory and electron-/phonon-dispersion, are in agreement with experimental results quantitatively. The scattering mechanism evolution from sole electron-electron scattering (un-doped BiOSe) to electron-phonon scattering (doped BiOSe) at high temperature (>60 K) is attributed to the net effect of decreased screened Coulomb-interaction and increased Fermi energy in halogen-doped BiOSe. This work may provide clues of physical origins of superior electrical/photoelectrical properties of BiOSe.