  Dynamical theories for piezotronic and piezo-phototropic devices are
incomplete. In this work, we aim to establish a theoretical method for
modelling dynamic characteristics of devices exhibiting these two emerging
phenomena. By taking the simplest piezotronic device-PN junction as an example,
we develop a small signal model and the united approach to analyze its
diffusion capacitance and conductance under both low and high frequency
external compressive stresses, which is different from the traditional
considerations that treat the piezopotential as a static value. Furthermore, we
expand the theory into piezo-phototronic devices e.g., a light emitting diode
(LED). The dynamic recombination rate and light emitting intensity are
quantitatively calculated under different frequencies of external compressive
stresses. The work complements existing works that only consider the static
cases. The work can shed light in future high frequency piezoelectronic devices
exploration.
