Sharp Resonance in a Metal–Oxide–Semiconductor Field-Effect Transistor with Multifinger Gate Configuration

Abstract

A sharp resonance has been observed at 300 MHz in the frequency dependence of the impedance measured for the backgate terminal of a metal–oxide–semiconductor field-effect transistor with a multifinger gate configuration under a certain bias condition. The quality factor was estimated to be over 1500 at the resonance, where the real part of impedance became negative. The results suggest that impact ionization periodically upsurges with a constant frequency. The sharpness of the frequency dependence has been discussed in terms of the feasible excitation of acoustic standing waves synchronized with impact ionization.

Relation between sharp resonance and bias condition in metal–oxide–semiconductor field-effect transistor with multiple gate configuration

“…4(b) is caused by a steep change in electric current. In particular, a steep decline in R indicates a steep increase in I sub , 6) which should be in accordance with an increase in the number of holes created per unit time through impact ionization. The sharp resonance therefore indicates that the impact ionization rate periodically and anomalously increased with the specific frequency incorporated with the increased number of LO phonons.…”

“…The author has proposed a new type of oscillator in his previous study, 6) in which a device based on metal-oxidesemiconductor field-effect transistor (MOSFET) with a multiple-gate configuration was fabricated using a typical CMOS process, and a sharp resonance with a quality factor 7,8) of Q > 1500 was preliminarily observed at 300 MHz in the frequency dependence of the impedance measured for the backgate terminal of the device. 6) In another study, 9) commonly detected from the backgate terminal, a steep increase in the substrate current I sub was observed in the gate voltage (V gs ) dependence measured for a device fabricated with a similar device configuration using the same CMOS process. The upsurge in I sub was observed in a limited narrow range of V gs between the threshold voltage V th and the saturation voltage V sat = V ds + V th , where V ds is the drain bias voltage.…”

“…Dummy gate electrodes (N dum = 24) were inserted between all active electrodes to increase the interelectrode spacing (d = 18 µm). 6,[11][12][13] The device has electrical terminals connected to the gate, drain, source, and backgate, as shown in Fig. 1(b).…”

“…X became positive in a narrow frequency range (¦f/f = 390 ppm, where ¦f is the frequency range with a positive X and f is the resonant frequency), implying that the device became inductive in this specific frequency range. The frequency dependence of impedance could not be explained, however, in terms of a series LCR equivalent circuit model 6) or the Butterworth-van-Dyke model, which is widely used for piezoelectric resonators. 18,19) Assuming that the acoustic wave causing the sharp resonance has a wavelength determined by the inter-finger spacing of gate electrodes (18 µm), as schematically shown in Fig.…”

“…The number of relevant LA phonons with a frequency of 427 MHz may be increased through a synchronized decay of LO phonons due to periodically arranged gate channels with equal intervals (18 µm) in the multiple-gate-finger configuration. 6,[9][10][11][12][13]24) In conclusion, from the backgate terminal of a MOSFET device with a multiple-gate configuration, the frequency dependence of impedance was measured under three typical categories of bias conditions. A sharp resonance with a quality factor of over 450 was detected at 427 MHz only under a saturation bias condition, whereas no resonances were observed under subthreshold and linear bias conditions.…”