Observation of excitonic features in ZnSe/ZnMgSSe multiple quantum wells by normalized Kelvin probe spectroscopy at low temperatures

The surface photovoltage spectra (SPS) of a series of ZnSe/ZnMgSSe multiple quantum wells of different well thickness (15-120 Angstrom) have been obtained as a function of temperature (48 K < T < 300 K) using a contactless Kelvin probe. In contrast to previous SPS measurements our data were taken using normalized incident light intensity. This normalization procedure has made it possible to fit the numerical derivative of the spectra (with respect to photon energy) to an appropriate lineshape factor to accurately determine the energies of the excitonic transitions. From the splitting between the fundamental conduction to heavy (11H)- and light (11L)-hole transitions as a function of well width we have confirmed the conduction band offset deduced by K. Shahzad et al. [Appl. Phys. Lett., 67, 659 (1995)]. We also have observed an interesting temperature dependence of the intensities of the 11H and 11L SPS features for different well widths. (C) 1997 Published by Elsevier Science Ltd.