Depletion‐mediated piezoelectric AlGaN/GaN resonators

Abstract

The electromechanical properties of an acoustic wave propagating in a piezoelectric media can be tuned by modulation of the resistivity of the piezoelectric material. This is readily available in piezoelectric semiconductor materials, wherein acoustic phonons and charge carriers can interact. In this work, we employ epitaxially grown AlGaN/ GaN heterostructures in bulk acoustic wave resonators with Schottky interdigitated transducers biased in the depletion region to study the interaction between piezoelectric strain and depletion charges. By modulating the impedance of the depletion layer upon application of DC voltages, we tune the acoustic properties of bulk-mode resonators and show significant Q enhancement as the result of a depletion force added to the piezoelectric actuation force. Furthermore, we compare the performance of such resonators with pure GaN piezoelectric resonators that have the same geometry but with the AlGaN layer removed. When integrated with AlGaN/GaN HEMTs (located on the acoustic cavity or next to the resonator), such resonators can be used as frequency references in oscillator circuits in radio frequency (RF) blocks or utilized in harsh environment sensing applications.

Design and analysis of high electron mobility transistor inspired: III-V electro-optic modulator topologies

“…The interaction can be enhanced by embedding such a device in a Fabry-Perot cavity as shown in figure 1(a). We analyze the effect of plasma dispersion effect due to the 2DEG carrier density modulated via external gate voltage applied to a depleted Schottky diode formed by the gate electrode and channel [30,31]. Intersubband (ISB) absorption due to TM polarized light in a quantum well is forbidden by selection rules at normal incidence [32].…”

Switchable Transducers in GaN MEMS Resonators: Performance Comparison and Analysis

“…Color coding coincides with the circuits shown in Figure 5. A non-switchable transducer in which the 2DEG is removed from the channel and acoustic energy is confined in a highly resistive GaN buffer is ideal for comparison because the performances of normally OFF switchable transducers are mainly determined by the depletion of 2DEG and phonon-electron scattering in the channel [31]. The results from the on-chip NS transducer with identical dimensions, number of IDTs, and phonon trap cavity are shown in Figure 5g-i, and extracted parameters are summarized in Table 1.…”

“…Switchable resonators integrated with AlGaN/GaN HEMTs for sensing acoustoelectric signals have been demonstrated to design frequency references in oscillator circuits [28][29][30]. The actuation mechanism of normally OFF switchable transducers consists of piezoelectric and electrostatic forces caused by a depletion of 2DEG in the ON state, which results in significant improvement of the quality factor [31]. Actuation without a separate control gate for DC bias in such transducers has previously been demonstrated [31][32][33].…”

“…The actuation mechanism of normally OFF switchable transducers consists of piezoelectric and electrostatic forces caused by a depletion of 2DEG in the ON state, which results in significant improvement of the quality factor [31]. Actuation without a separate control gate for DC bias in such transducers has previously been demonstrated [31][32][33]. In our previous work, we have realized a switchable Lamb mode resonator with a Schottky control gate design showing improved transduction [34].…”

Ultrahigh Frequency Nanomechanical Piezoresistive Amplifiers for Direct Channel-Selective Receiver Front-Ends

“…Piezoelectric devices, on the other hand, provide a significantly lower insertion loss but lack in quality factor (e.g., 500–4000 ,, ). There have been recent efforts to develop on-chip active resonant components by integrating field effect transistors (FETs) within electromechanical devices. − Such devices have not been able to meet the SDR performance requirements either.…”