Structure asymmetry effects in the optical gain of piezostrainedInGaN quantum wells

摘要

We investigate the effects of structural asymmetry on thenelectronic and optical properties of indium gallium nitride (InGaN)nquantum wells (QW's). Using a pulsed current excitation technique,nspectral blue shift as large as 80 meV is observed in a strained 3.0-nmnIn0.2Ga0.8N QW as the pulsed current increasesnfrom 1 mA to 1 A. Based on a self-consistent calculation, we are able tonquantify a gain competition process among the interactions ofnpiezoelectricity, many-body, charge screening, and band filling effects.nSuch interactions are shown to provide a mechanism for shaping the QWnconfined potential such that superior carrier confinement and chargenscreening of the piezoelectric field can be obtained in the asymmetricnInGaN QW. At high carrier injection ofnNinj>2×1019 cm-3, a tenfoldnincrease in the TE-polarized optical gain can be achieved by using thenasymmetric GaN-InGaN-AlGaN QW instead of the symmetric InGaN-AlGaN QW.nDue to the diminishing of piezoelectricity-induced quantum-confinednStark effect, the calculated optical gain spectra of the asymmetricnInGaN QW exhibit a spectral blue shift with respect to those of thensymmetric InGaN QW