Structure in the flicker-noise power spectrum ofn-InSb

We have measured the power spectrum of flicker noise in high-purity, single-crystal $n$-InSb at 76 K in the frequency range 0.1 Hz-10 kHz. The power spectrum can be interpreted as a superposition of two noise spectra. One of them is $\frac{1}{f}$ like at frequencies above a cutoff frequency $f_0$ which is on the order of a few hundred Hz, while at frequencies below $f_0$ it appears to level off to a constant value. The second spectrum is dominant at frequencies well below $f_0$ and behaves as $\frac{1}{f}$. Noise power much smaller than that predicted by the Hooge relation, $S_{\delta V}=\frac{\alpha V^2}{\mathrm{NF}}$, is observed. Also it is found that chemical treatments of the surface have a strong influence on the magnitude of the measured flicker noise.