Design and characteristics of staggered InGaN quantum-well light-emitting diodes in the green spectral regime

Staggered InGaN quantum wells (QWs) are investigated both numerically and experimentally as improved active region for light-emitting diodes (LEDs) emitting at 520-525nm. Based on a self-consistent six-band k·p method, band structures of both two-layer staggered In_xGa_1-xN/ In_yGa_1-yN QW and three-layer staggered In _yGa_1-yN/In_xGa_1-xN/In _yGa_1-yN QW structures are investigated as active region to enhance the spontaneous emission radiative recombination rate (R_sp) for LEDs emitting at 520-525nm. Numerical analysis shows significant enhancement of R_sp for both two-layer and three-layer staggered InGaN QWs as compared to that of the conventional In_zGa_1-zN QW. Significant reduction of the radiative carrier lifetime contributes to the enhancement of the radiative efficiency for both two-layer and three-layer staggered InGaN QW LEDs emitting at 520-525nm. Three-layer staggered InGaN QW LEDs emitting at 520-525nm was grown by metal-organic chemical vapour deposition (MOCVD) by employing gradederature profile. Power density-dependent cathodoluminescence (CL) measurements show the enhancement of peak luminescence by up to 3 times and integrated luminescence by 1.8-2.8 times for the three-layer staggered InGaN QW LED. Electroluminescence (EL) output power of the staggered InGaN QW LED exhibits 2.0-3.5 times enhancement as compared to that of the conventional InGaN QW LED. The experimental results show the good agreement with theory.