Structure asymmetry effects in the optical gain of piezostrained InGaN quantum wells

We investigate the effects of structural asymmetry on the electronic and op tical properties of indium gallium nitride (InGaN) quantum wells (QW's), Us ing a pulsed current excitation technique, spectral blue shift as large as 80 meV is observed in a strained 3.0-nm In0.2Ga0.8N QW as the pulsed curren t increases from 1 mA to 1A. Based on a self-consistent calculation, me are able to quantify a gain competition process among the interactions of piez oelectricity, many-body, charge screening, and band filling effects. Such i nteractions are shown to provide a mechanism for shaping the QW confined po tential such that superior carrier confinement and charge screening of-the piezoelectric field can be obtained in the asymmetric InGaN QW. At high car rier injection of N-inj > 2 x 10(19) cm(-3), a tenfold increase in the TE-p olarized optical gain can be achieved by using the asymmetric GaN-InGaN-AlG aN QW instead of the symmetric InGaN-AlGaN QW. Due to the diminishing of pi ezoelectricity-induced quantum-confined Stark effect, the calculated optica l gain spectra of the asymmetric InGaN QW exhibit a spectral blue shift wit h respect to those of the symmetric InGaN QW.