Diffusion and recombination 1/f noise in long n+-p Hg1—xCdxTe diodes

1/f noise in long n⁺-p Hg1-xCdxTe diodes with x = 0.30 is studied at 193 K. The 1/f noise is considered to be generated by diffusion and recombination fluctuations. A distinction is made between cases a (all minority carriers contribute to the 1/f noise) and b (only the excess minority carriers contribute to the 1/f noise). Measurements on long nonplanar diodes show that case a is valid, indicating that all minority carriers contribute equally to the 1/f noise; this should be valid for any long-junction device in which the current flow is by diffusion and recombination of minority carriers. The lifetime τnof the electrons in the p-region is measured by the input impedance method, and the Hooge parameter αHof the device is evaluated. τnis of the order of 10^-6to 10^-7s and depends somewhat on bias. Near zero bias αHis of the order of 5 × 10^-3in close agreement with Handel's coherent state 1/f noise theory, which yields αH= 4.6 × 10^-3. Due to the nonplanar geometry of the studied diodes, the measurement of τnis not always equally reliable. Larger values of τnare accompanied by larger values of αH, because the noise measurements give αH/τn, and its value practically independent of bias. We also evaluated τnby putting αH= 4.6 × 10^-3; the τnvalues are then much closer and agree rather well with Honeywell lifetime tables. Preliminary measurements at 113 K also indicate coherent state 1/f noise, whereas data at 273 K give αH= 5 × 10⁵, in agreement with the Umklapp 1/f noise theory.