Effect of graded Al composition in w-shaped quantum wells and Δ-shaped quantum barriers on performance of AlGaN based UV-C light emitting diodes

•W-shaped QWs and Δ-shaped QBs enhances IQE from 31% to 62%.•Efficiency droop reduced from 11% to 3%.•Composition pulling effect reduced leads to diminished polarization between the epitaxial layers of active zone.•Carrier wave function overlap increased from 18% to 39%.•Blue shift in wavelength is experienced from 275 nm in LED-A to 272 nm in LED-A.•Electron leakage current density reduced in p-region.•Hole flux increased in active zone.