FREQUENCY DEPENDENCE OF THE DEBYE LENGTH IN COMPENSATED EXTRINSIC PHOTOCONDUCTORS

A frequency‐dependent Debye length is derived for the case of unipolar photoconductivity in a compensated extrinsic photoconductor. The frequency dependence is associated with the finite time necessary to establish equilibrium between an excess free carrier density and a deficit ionized impurity density in the case of bipolar recombination. The frequency dependence of the Debye length leads to a frequency‐dependent effective drift length $$L_{\mathrm{eff}}\mathrm{(\omega )=E\mu }{\left\{\frac{1}{{\tau }_{\rho }}\left[\text{1+}\frac{n_0}{p_{\text{0′}}}\left(\text{1+}\frac{{\omega }^2{\tau }^2{n}_0^2}{p_0^2}\right)\right]{\mathrm{+\omega }}^2\tau {\left(\frac{n_0}{p_0}\right)}^2{\left(\text{1+}\frac{{\omega }^2{\tau }^2{n}_0^2}{p_0^2}\right)}^{\text{−1}}\right\}}^{\text{−1}}\mathrm{\hspace{0.17em}(p\hspace{0.17em}}\mathrm{type})$$ which can be used to explain the sweepout results obtained by Williams with mercury‐doped germanium photoconductors under high resistivity conditions.