Modified InGaN/GaN quantum wells with dual-wavelength green-yellow emission

Energy band engineering by indium pretreatment of the bottom GaN barriers and control of the growth temperature profile for the InGaN active layers were employed to improve the green-yellow emitting InGaN/GaN quantum well (QW). The modified InGaN/GaN QWs were investigated by various characterization techniques and demonstrated to be of good interface abruptness and well-defined indium concentration profile, composed of 0.52 nm In_0.35Ga_0.65N “wetting layer,” 1.56 nm In_0.35-0.22Ga_0.65-0.78N graded layers, and 1.56 nm In_0.22Ga_0.78N layer along the growth direction. Broad-band dual-wavelength green-yellow emission at about 497 and 568 nm was observed and attributed to the major contribution of enhanced interband transitions from the first and second quantized electron states “e1” and “e2” to the first quantized hole state “h1.” With the modified QW structure, electron overflow loss would be suppressed by filling of the excited electron state with electrons at high carrier injection density and reduction in polarization-induced band bending. APSYS simulation shows efficiency and droop improvements due to the enhanced overlapping of electron and hole wave functions inside the modified InGaN active layers, and the enhanced interband transitions involving the excited electron state.