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Molecular beam epitaxial GaAs layers of electron concentration 1.69×1017 cm3, and various thicknesses d=0.25, 0.50, 1.00, and 2.00 μm, have been grown on semi‐insulating GaAs substrates and characterized by the Hall effect and capacitance‐voltage (CV) techniques. A plot of sheet Hall concentration ns vs d gives accurate values of (NDNA) and (ws+wi), the sum of the surface and interface free‐carrier depletion widths, respectively. The CV measurements verify the value of NDNA, and also give a good estimate of wi. By comparing the value of wi with depletion theory, it is shown unambiguously that the interface depletion is mainly due to interface states, of concentration 1.2×1012 cm2 (below midgap). This result has important technological implications.


Copyright © 1990, American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 56.7, and may be found at



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