Constructive and comprehensive studies on the advantages of using staggered InxGa1-xN/InyGa1-yN QWs in LEDs

A hurdle encountered in the InGaN/GaN LED, is, that the overlap of electrons and holes decreases significantly under certain conditions which deteriorates the performance of the LED. Several methods are being studied for increasing the overlap of electrons and holes of which introduction of a staggered InGaN/GaN QW, in place of the rectangular QW seems promising. In this paper we have studied comprehensively, different forms of the staggered QW; single sided and symmetric, with different Indium compositions in the well. Computations have been carried out through the self-consistent solutions of Schrödinger and Poison equations. We have studied the band structures, fields, the carrier distributions, the transition energies and the overlap of the electron and hole wave functions with current densities. It has been found that the overlap of electrons and holes increases significantly for the staggered QWs at the same current. The best results are obtained for the symmetrically staggered QWs, where the overlap increases even up to three times that of the rectangular QW and using this structure the operating current may be decreased by more than two orders of magnitude to obtain the same transition energy. The theoretical and computational results will be presented with suitable discussions.