Abstract
To manufacture faster electron devices, the industry has entered into the nanoscale dimensions and Terahertz (THz) working frequencies. The discrete nature of the few electrons present simultaneously in the active region of ultra-small devices generate unavoidable fluctuations of the current at THz frequencies. The consequences of this noise remain unnoticed in the scientific community because its accurate understanding requires dealing with consecutive multi-time quantum measurements. Here, a modeling of the quantum measurement of the current at THz frequencies is introduced in terms of quantum (Bohmian) trajectories. With this new understanding, we develop an analytic model for THz noise as a function of the electron transit time and the sampling integration time, which finally determine the maximum device working frequency for digital applications. The model is confirmed by either semi-classical or full- quantum time-dependent Monte Carlo simulations. All these results show that intrinsic THz noise increases unlimitedly when the volume of the active region decreases. All attempts to minimize the low signal-to-noise ratio of these ultra-small devices to get effective THz working frequencies are incompatible with the basic elements of the scaling strategy. One can develop THz electron devices, but they cannot have ultra-small dimensions. Or, one can fabricate ultra-small electron devices, but they cannot be used for THz working frequencies.
Highlights
To manufacture faster electron devices, the industry has entered into the nanoscale dimensions and Terahertz (THz) working frequencies
The problem affects small-volume devices customarily developed by the electronics industry to continue with the ongoing scaling strategy, where the information is manipulated by means of electrical signals based on the motion of charge carriers and associated currents
We show that the THz noise grows when the volume of the active region decreases
Summary
We test the previous predictions about the THz noise for a realistic ultra-small device, without most of the simplifying assumptions that we have used in the analytical and previous simulations sections. We remark that the results presented here will not be obtained from an ensemble average over different experiments, since when an electron device is working in a real application, there is no interest in mean values of the current in different experiments, we are just interested on the time interval that the measurement equipment needs to clearly discern if our single electron device is in L1 or in L2. No ergodic argument can be invoked in the type of THz scenarios described here With this information, we can obtain the time averaged current and its associated noise (in the same way as it was done in Fig. 6) for both time intervals (before and after switching the gate voltage). Making measurements with a lower acquisition/integration time (or with a higher working frequency) to get a faster application would imply an intolerable THz noise
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