Comparative study on passivation of GaAs<SUB>0.86</SUB>P<SUB>0.14</SUB>/Al<SUB>0.6</SUB>Ga<SUB>0.4</SUB>As near-surface quantum well

The authors report a comparative study on ex situ passivation of a near-surface GaAs0.86P0.14/Al0.6Ga0.4As quantum well using various sulfide solutions and nitrogen plasma treatments. The built-in surface electric field is changed via band bending by applying various surface passivation conditions. The band bending is measured using x-ray photoelectron spectroscopy. Reduction in surface electric field in the range of 10-35 kV/cm is observed depending on different passivation conditions. The photoreflectance spectra show enhancement in intensity and blueshift of ~3 meV accompanied by significant reduction in the broadening parameter of the observed e1-lh1 transitions. Among all the methods studied here, passivation by Na2S⋅xH2O is found to be most effective as it removes the native oxide layer completely leading to almost flat band condition