Photoluminescence studies of <100>-and <111>-grown indium gallium arsenide strained single quantum wells under hydrostatic pressure



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Texas Tech University


InGaAs/GaAs strained quantum wells are of technological importance and current scientific interest. Most of this interest stems from variations achieved in the electronic band structure due to the combined effects of alloying, strain and quantum confinement. When these heterostructures are grown along non-[001] directions, a strain-induced piezoelectric field is present within the coherently strained layer. This interesting effect significantly complicates the optical transitions. While these novelly-grown-strained quantum wells have already been successfully fabricated into optoelectronic devices, the effects of the piezoelectric field on fundamental recombination processes is not well understood. Further, the alignment in (lll)-grown. In GaAs/GaAs heterostructures has not been established. In this work, photoluminescence spectroscopy is combined with hydrostatic pressure to examine band edge radiative recombination from simultaneously grown single quantum well pairs with different growth axis orientations: (100) and (111)A. The (l00)-grown quantum well is used as a basis for comparing the optical response and pressure dependence of the (111)-grown well. .Ml photoluminescence measurements were done with the samples at 77K. Ambient pressure work established the magnitude of the strain induced piezoelectric fic4d within the (111)-grown quantum well. The experimentally determined value of 72 kV/cm agrees with the value computed using first-order elastic theory. Pressure studies precisely establish a valence band discontinuity for the 100 grown well of 61 meV which corresponds to an unstrained bandgap off-set ratio of ÄEc : ÄEv = 0.75 : 0.25. By carefully monitoring the nonlinear optical response of the photoluminescence from the (lll)-grown quantum well under pressure, reliable identification of high pressure photoluminescence emission processes was accomplished. The first time observation of the above crossover indirect emission from the (HI)- grown quantum well allowed for the establishment of limits on the valence band discontinuity of !^100 to 130 meV.