Method and apparatus for determining characteristic electrical material parameters of semi-conducting materials

A method for determining characteristic electrical properties of semi-conducting materials wherein the time or frequency dependent electrical impedance Z(t) or Z(.omega.), respectively, or admittance Y(t) or Y(.omega.), respectively, is measured, comprising the steps of establishing a finite, positive (n-type material) or negative (p-type material) difference in the chemical potential between the inner and the surface of the material or between the inner of the material and the metal electrode--material surface interface layer, thereby causing the formation of depletion regions near the electrical contacts and by using the effect of this established difference in the chemical potential on the measured electrical impedance or admittance the step of determining from this measured electrical impedance or admittance one, more or all of the following electrical parameters f the material:

• the difference .DELTA..mu..sup.ch in chemical potential,
• the dielectric constant .epsilon.,
• the density N of majority mobile charge carriers,
• the density N.sub.min of minority mobile charge carriers,
• the electrical mobility .mu. of majority mobile charge carriers,
• the electrical mobility .mu..sub.min of minority mobile charge carriers,
• the emission and capture rates E.R and C.R, respectively, for mobile positive and negative charge carriers characterizing the effect of surface and bulk localized states within the band gap (Eg), when they are present, on the electrical transport and the measured electrical impedance, whereby the determination of the electrical parameters of the material is carried out by solving a system of equations for the total charge density .rho.(x,t) consisting of the mobile negative and positive charge densities and localized negative and positive charge densities in the material supplemented with initial and boundary conditions, where the space-time development of .rho.(x,t) determines the electric current running in the external circuit in response to the applied electric voltage thereby defining the electrical complex impedance Z.sub.s (.omega.) of the material.