Highly sensitive piezotronic pressure sensors based on undoped GaAs nanowire ensembles

Abstract

Semiconducting piezoelectric materials have attracted considerable interest due to their central role in the emerging field of piezotronics, where the development of a piezo-potential in response to stress or strain can be used to tune the band structure of the semiconductor, and hence its electronic properties.This coupling between piezoelectricity and semiconducting properties can be readily exploited for force or pressure sensing using nanowires, where the geometry and unclamped nature of nanowires render them particularly sensitive to small forces. At the same time, piezoelectricity is known to manifest more strongly in nanowires of certain semiconductors. Here, we report the design and fabrication of highly sensitive piezotronic pressure sensors based on GaAs nanowire ensemble sandwiched between two electrodes in a back-to-back diode configuration. We analyse the current-voltage characteristics of these nanowire-based devices in response to mechanical loading in light of the corresponding changes to the device band structure. We observe a high piezotronic sensitivity to pressure, of ~7800 meV/MPa. We attribute this high sensitivity to the nanowires being fully depleted due to the lack of doping, as well as due to geometrical pressure focusing and current funnelling through polar interfaces.

Effect of the Uniaxial Compression on the GaAs Nanowire Solar Cell

“…Since the piezoelectric effect led to the formation of the opposite charges at the top and bottom planes of the NW, fixed charges, i.e., Q f and −Q f , were set at the GaAs/Si and GaAs/top contacts, respectively (Figure 2b). The positive charge was always at the GaAs/Si interface because it was induced at the bottom of the GaAs NW grown in the 111B direction under compression [23]. The Q f charges per 1% strain for the zinc blende and wurtzite GaAs are presented in Table 1.…”

“…For GaAs (111) diodes, external deformation was shown to shift the Schottky barrier height [22]. Recently, highly sensitive piezotronics pressure sensors were developed based on undoped zinc blende GaAs NWs and demonstrated a high piezotronic sensitivity to pressure of 7800 meV/MPa [23]. The growth of zinc blende or wurtzite GaAs NWs on Si substrates would also be assumed to induce piezoelectric polarization due to the strain created by the difference between the GaAs and Si lattice constants [24], but the impact of such polarization on the electrical properties of GaAs/Si solar cells has not yet been studied.…”

Measuring the Optical Absorption of Single Nanowires

“…[3], while for the growth of the WZ NWs see Ref. [37]. Both types of GaAs NWs have an average diameter of 70 ± 5 nm, as measured using SEM.…”

Enhanced piezoelectricity and electromechanical efficiency in semiconducting GaN due to nanoscale porosity

“…These applications are referred to as piezotronic/photo-piezotronic. [6][7][8][9][10][11] III-Ns and non-nitride III-Vs are attracting increased attention in piezotronics 5,12 due to their mature processing, possible silicon integration and span of desired electronic and optical properties. [13][14][15] Porosification has been used as a processing tool to control the optical properties of GaN [16][17][18][19] as well as its mechanical properties.…”