Electric field dependence of mobility fluctuation 1/f; noise in elemental semiconductors

It is shown that Bosman's empirical formula α(E) = α(0)/1 + (E/E_c′)²] for the field dependence of Hooge's parameter can be explained if it is assumed that only the low-field value μ_aco of the acoustical mobility μ_ac fluctuates and that $\text{μ}{}_{\mathrm{ac}}\text{= μ}{}_{\mathrm{aco}}\text{1 + (E/E}{}_{\mathrm{c}}\text{′)}{}^2\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$.