The functional switching on the operating modes of a piezoelectric semiconductor bipolar junction transistor via mechanical loadings

Abstract

A nonlinear model was developed on piezoelectric bipolar junction transistors (PS-BJTs) subjected to mechanical loadings by disregarding the assumption of low injection and the approximation of depletion layer. It was found that a PS-BJT subjected to different mechanical loadings can exhibit distinct carrier flow directions, for example, a remarkable transition for an n+pn-type PS-BJT from a transistor unit with amplification capability to two parallel connected PN junctions by applying a pair of lateral tensile or compressive stresses at the emitter and collector interfaces. Further in-depth analysis revealed that shielding effect produced by base region carriers greatly varies according to different loading mode, which leads to changing degrees of mechanical reconstruction on emitter junction barrier. Consequently, an artificial electron pathway (AEP) is formed at the emitter junction by a specific loading configuration. It is just due to the form change of AEP to produce distinct carrier flow directions, which can realize multifunctional switching of electronic devices. In addition, we also found an interesting phenomenon that an AEP can be directly constructed to penetrate the emitter junction by applying mechanical loadings in the longitudinal direction such that electrons in emitter region can travel across the emitter interface directly to the collector region without regulated by the base current. Under that situation, the PS-BJT resembles a parallel combination of a PN junction and an NN junction. This research provides novel insights into the mechanical modulation of piezoelectric electronic devices and the design of novel logic circuits.