Photoluminescence microscopy imaging of tensile strained In1-xGaxAsyP1-y/InP quantum wells grown by low-pressure metalorganic vapor phase epitaxy

The optical properties of tensile strained In1-xGaxAsyP1-y/InP single quant um wells grown by low-pressure metalorganic vapor phase epitaxy were invest igated by the real-time integrated photoluminescence microscopy imaging tec hnique at room temperature. The photoluminescence microscopy images reveale d the presence of a large number of nonradiative centers (dark spots). The dark spot density was found to be strongly dependent on the tensile strain magnitude, barrier type material and cap layer thickness. High tensile stra in values and thin InP cap layers resulted in an increased density of dark spots. Tensile strained structures employing lattice-matched quaternary bar riers instead of InP barriers exhibited reduced defect density. Our results indicate that these defects are mainly localized close to or at the interf ace between the quaternary well and the upper barrier material. The reducti on of the number of defects correlates quantitatively with increased radiat ive recombination efficiency in these structures. (C) 1999 American Institu te of Physics. [S0021-8979(99)08813-1].