Dip-shaped InGaN/GaN quantum-well light-emitting diodes with high efficiency

Optical properties of dip-shaped InGaN/GaN quantum well (QW) light-emitting diodes are investigated using the multiband effective-mass theory. These results are compared with those of conventional and staggered InGaN/GaN QW light-emitting diodes. In the case of a dip-shaped QW structure, the carrier density dependence of the transition wavelength is reduced due to a relatively small internal field effect. Also, we observe that the heavy-hole effective mass around the topmost valence band is greatly reduced with the inclusion of the dip-shaped layer. The spontaneous emission peak of a dip-shaped QW structure is shown to be larger than that of a staggered QW structure or a conventional QW structure. This is mainly due to the fact that a dip-shaped QW structure has larger optical matrix elements produced by Kane's parameter.