Nearly Universal $\hbox {1}/f^{2}$ Spectrum of Mobility Fluctuation Noise in a Quantum Wire at Radio and Microwave Frequencies

We have studied the noise power spectrum associated with mobility fluctuations of hot carriers in a GaAs quantum wire in the frequency range of 20 MHz-50 GHz using ensemble Monte Carlo simulation. This frequency range is outside the regime where a noise peak occurs in quantum wires due to well-known streaming oscillations in the carrier drift velocity. In this frequency range, the noise power spectrum is found to exhibit a nearly universal 1/f^α dependence, where f is the frequency. The exponent α remains remarkably constant over a wide range of electric field and temperature, and varies between 1.96 and 1.98 as the driving electric field is varied from 500 V/cm to 10 kV/cm at two different temperatures of 30 and 77 K. The constancy of α and its value of ~ 2 may be related to the nature of electron-phonon interactions in quantum wires.