PHOTOLUMINESCENCE SPECTROSCOPY OF NEAR-SURFACE QUANTUM-WELLS - ELECTRONIC COUPLING BETWEEN QUANTIZED ENERGY-LEVELS AND THE SAMPLE SURFACE

Photoluminescence (PL) measurements have been used to examine the infl uence which the proximity of the sample surface bears on the radiative recombination occurring within a near-surface quantum well (QW). The InxGa1-xAs/GaAs system exhibits dramatic attenuation in PL intensity f or surface barriers below 75 angstrom in thickness, without any signif icant shift in PL peak energy. However, as the GaAs surface barrier is reduced to zero, both In0.26Ga0.74As/GaAs and In0.1Ga0.9As/GaAs QWs r eveal the development of an additional PL feature at an energy which c oincides with that expected for direct band-to-band recombination with in the strained InxGa1-xAs layer. PL measurements for chemically etche d Al0.3Ga0.7As/GaAs near-surface QWs also show a lack of shift in PL p eak energy, as the outer layer is thinned gradually.