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

1/f noise in long n
⁺
-p Hg
1-x
Cd
x
Te 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 τ
n
of the electrons in the p-region is measured by the input impedance method, and the Hooge parameter α
H
of the device is evaluated. τ
n
is of the order of 10
^-6
to 10
^-7
s and depends somewhat on bias. Near zero bias α
H
is of the order of 5 × 10
^-3
in close agreement with Handel's coherent state 1/f noise theory, which yields α
H
= 4.6 × 10
^-3
. Due to the nonplanar geometry of the studied diodes, the measurement of τ
n
is not always equally reliable. Larger values of τ
n
are accompanied by larger values of α
H
, because the noise measurements give α
H
/τ
n
, and its value practically independent of bias. We also evaluated τ
n
by putting α
H
= 4.6 × 10
^-3
; the τ
n
values 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 α
H
= 5 × 10
⁵
, in agreement with the Umklapp 1/f noise theory.