Structural and electrical properties of Ni- and Mg-doped p-type α-AlCrO3 wide bandgap semiconductor

Abstract

In this thesis, we explore α-AlCrO3 as a wide bandgap semiconductor oxide potential candidate for p-type doping through the strategic doping of divalent cations Ni2+ and Mg2+ at the Al3+ site. The host material α-(AlxCr1−x)2O3 (0 ≤ x ≤ 1) exhibits a rhombohedral structure (R-3c) with a tunable bandgap ranging from 3.4-5.3 eV and strong hybridization between Cr 3d and O 2p orbitals that makes it an ideal host for p-type conductivity engineering. Single-phase polycrystalline samples of -Al1-xBxCrO3, where B = Ni2+, Mg2+ and 0≤ x ≤ 0.02 were synthesized via the solid-state reaction method. Structural integrity and doping solubility were confirmed through synchrotron-based X-ray diffraction and Le-Bail refinement. Optical characterization via DRS reveals that with Ni doping no changes in intrinsic band transitions and thus by observed no change in bandgap energy. The electrical charge carriers transport phenomenon was thoroughly investigated using complex impedance spectroscopy (CIS). Both Ni2+ and Mg2+ doping led to significant reductions in energy activation and resistance with superior performance observed at x = 0.01.