Explicit forms of the Langevin noise sources due to both intraband and interband scattering are given for the Boltzmann transport equations with the relaxationhyphen;time approximation in nondegenerate semiconductors. A generalized formula for the shorthyphen;circuited noise currents, which holds in both homogeneous and nonhomogeneous onehyphen;dimensional nondegenerate semiconductors, is derived in a unified manner by solving the Langevinhyphen;type Boltzmann transport equations. From this generalized noise formula the shorthyphen;circuited noise currents for thermal noise, generationhyphen;recombination noise, and 1/fnoise in a homogeneous nondegenerate semiconductor bar are calculated. It is shown that for homogeneous nondegenerate semiconductors, Nyquistrsquo;s theorem always holds both at thermal equilibrium and under an applied dc electric field with either intraband scattering or interband scattering dominant. Generationhyphen;recombination noise is shown to be caused by the electrons or holes whose scattering mechanism is dominated by intraband scattering, and the derived generationhyphen;recombination noise formula is the same as the one derived by the conventional methods. It is also shown that 1/fnoise may be caused by a very small number of electrons (or holes) lying just around the bottom of the conduction band (or the top of the valence band) when interband scattering is dominant over intraband scattering for these electrons (or holes). The contribution of these small number of electrons (or holes) to the electrical conductivity is negligible because of the smallness of the number of these carriers. The derived 1/fnoise formula has the same functional form as the Hoogersquo;s empirical relation lsqb;Physica83, 14 (1976)rsqb;.
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