High spontaneous emission rate asymmetrically graded 480 nm InGaN/GaN quantum well light-emitting diodes

Spontaneous emission property of an asymmetrically graded 480 nm InGaN/GaN quantum well (QW) is investigated via k ⋅ p theory. Comparing to rectangular QW, band profiles of the graded QW change into parabolalike due to the variation of internal piezoelectric field along the growth direction, and the spontaneous emission rates of the graded QW are three times larger than rectangular case under various carrier densities. This can be attributed to the fact that the graded QW has much larger matrix element ( M e ) n m σ ( k t ) than rectangular QW considering that the wave function overlap of the graded QW is less affected by the quantum confined Stark effect.