Raman scattering determination of free-carrier concentration and surface space-charge layer in <100> n-GaAs

Shen, H.; Pollak, Fred H.; Sacks, R. N.
October 1985
Applied Physics Letters;10/15/1985, Vol. 47 Issue 8, p891
Academic Journal
We have used Raman scattering as a nondestructive, contactless method for determining not only the free-carrier concentration N but also the width of the space-charge layer in <100> n-GaAs with 4×1017 cm-3≤N≤1×1019 cm-3 using as an excitation several different wavelengths of an Ar+ laser. By comparing the intensity at different wavelengths of the uncoupled longitudinal optic phonon mode originating in the space-charge layer with the signal from a piece of undoped <100> material, it is possible to experimentally evaluate the width of the depletion layer Ls. We find that there is very good agreement between the experimental values and those obtained from a generalized theory for both degenerate and nondegenerate materials. Thus, these experimental results demonstrate that for <100> III-V semiconductors, Raman scattering can be used as a contactless method to determine the width of the space-charge region for carrier concentrations up to 1×1019 cm-3.


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