Polarization-sensitive Schottky photodiodes based on a-plane ZnO/ZnMgO multiple quantum-wells

Abstract

Light polarization-sensitive UV photodetectors (PSPDs) using non-polar a-plane ZnMgO/ZnO multiple quantum wells grown both on sapphire and ZnO substrates have been demonstrated. For the PSPDs grown on sapphire with anisotropic biaxial in-plain strain, the responsivity absorption edge shifts by ΔE ∼ 21 meV between light polarized perpendicular (⊥) and parallel (||) to the c-axis, and the maximum responsivity (R) contrast is (R⊥/R||)max ∼ 6. For the PSPDs grown on ZnO, with strain-free quantum wells, ΔE ∼ 40 meV and (R⊥/R||)max ∼ 5. These light polarization sensitivities have been explained in terms of the excitonic transitions between the conduction and the three valence bands.