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

Abstract

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 L_s. 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.