Monte Carlo analysis of electronic noise in semiconductors under sub‐terahertz cyclostationary mixed fields

Abstract

This paper reports the results of Monte Carlo simulations of electronic noise in a GaAs bulk driven by two mixed high-frequency large-amplitude periodic electric fields. Under these conditions, the system response shows some peculiarities in the noise performance, such as a resonant-like enhancement of the spectra near the two frequencies of the applied fields. The relations among the frequency response and the velocity fluctuations as a function of intensities and frequencies of the sub-terahertz mixed excitation fields have been investigated.1 Introduction The sensitivity of semiconductor based devices is strongly affected by the presence of noise, which sets the lower limit for signal detection in electronic circuits. Much effort has been devoted to achieve a physical understanding of microscopic noise mechanisms within solid-state electron devices and to model electronic noise under small-signal conditions. However, when real materials and devices are used at very high frequencies around the THz region (broadband services, mobile network, oscillators, mixers, etc), they exhibit strong nonlinearities, such as the appearance of hysteresis cycle in their characteristics and the generation of harmonics. High-order harmonic generation and frequency mixing effects have been investigated in low-doped bulk semiconductors subject to far-infrared intense electric field [1,2]. These studies have shown that, under wave-mixing signal regime an enhancement of the harmonic generation can be produced. This fact can be useful for possible applications of semiconductor devices as sources of THz radiation. Nevertheless, the extraction of these harmonics is limited by the intrinsic high-frequency noise of the nonlinear medium, which can mask the generated high-order harmonics. Therefore, under cyclostationary conditions, these dynamical effects have to be considered and nonlinear analysis of noise must be performed. Previous studies have analysed the electronic noise under large-signal conditions for the case of bulk semiconductor and simple devices [3][4][5][6]. However, to our knowledge, the noise behaviour in semiconductor systems has not been investigated in the presence of a mixing of coherent electromagnetic radiations of commensurate frequencies. The complex nonlinear phenomena involved in the wave mixing regime make essential an accurate simulation and analysis of the noise performance in semiconductor materials. The paper is organised as follows: in Sect. 2 a brief description of the model used in the many-valleys anisotropic Monte Carlo code and the theoretical approach used for fluctuations estimation are presented; in Sect. 3 the main results of calculations are reported and discussed and final conclusions are given in Sect. 4.

Wave-mixing effects on electronic noise in semiconductors

“…In a previous paper we have examinated the dependence of the frequency response and of the velocity fluctuations by the intensities of the mixed excitation fields with the aim to establish if the wave-mixing could cause an enhancement or a suppression of the noise level. We have found that the level and the peaks in the noise spectra are very sensitive to the amplitude of the excitation signals [7].…”

External Noise Effects on the Electron Velocity Fluctuations in Semiconductors

“…The spectral density of the electron velocity fluctuations in a n-type GaAs bulk undergoes critical modifications under the action of two mixed highfrequency large-amplitude periodic electric fields [1][2][3]. In particular, recent studies based on Monte Carlo simulations have shown that the total power of the intrinsic noise is very sensitive to the amplitude and the frequency of the excitation signals and that wave-mixing conditions may give rise to a mere redistribution, an enhancement or a suppression of the noise level, depending on the constructive interplay between the two excitation fields.…”