InGaN-based light-emitting diodes with Al content graded p-AlxGa1-xN top contact layer

This study demonstrates a GaN-based light-emitting diode (LED) structure with an Al composition, graded p-Al x Ga 1− x N top contact layer as the electron-blocking layer (EBL). Experimental results showed that the LEDs with graded EBL layer exhibited lower forward voltage ( V f ) and higher output power (L op ) than conventional LEDs with constant Al composition in the EBL. The lower V f is attributed to the relatively higher hole concentration caused by the polarization field in the graded AlGaN EBL. In addition to the improved hole concentration, the higher L op is also due to the improved electron confinement caused by the graded EBL. • GaN-based light-emitting diode (LED) structure possessed an Al composition graded p-AlxGa1-xN top contact layer. • Polarization field in the graded AlxGa1-xN EBL causes the relatively higher hole concentration. • Graded AlGaN EBL could effectively mitigate electrons to overflows to the p-GaN. • LEDs with the graded AlGaN EBL exhibited higher efficiency than conventional LEDs with constant Al in the EBL.