Ion implanted double-drift impatt diodes: Low-frequency noise

The low-frequency open circuit noise spectral density, S(f) = <V²>/Δf, of an avalanching junction can be represented by S(f) = a²VB²/Iowhere VB, Io, and a²are the reverse voltage, current, and a factor dependent on the ionization coefficients, respectively. For single-drift p⁺-n or n⁺-p silicon diodes A/Hz. However, for symmetric p-n junctions, e.g., a double-drift IMPATT diode, the first-order theory predicts A/Hz. Low-frequency noise measurements were made on a double-drift IMPATT to confirm the inverse current dependence and to experimentally determine the magnitude of a².