Electrically Tunable Piezotronic Transistor by Coupling Interface Polar Symmetry and Strain Gradient

Piezotronics, which enables mechanical stimuli to actively shape adaptive and seamless interactions between electronic systems and ambient environments, is becoming increasingly valuable in the Internet of Things, human-machine interfaces, and wearable electronics. Interface-dominated polarization underpins efficient electromechanical transduction in piezotronic sensors; however, it enforces limited performance tunability and hampers multifunctional applications. Here, we use a macroscale tip-induced strain gradient to trigger a bulk-dominated polarization in GaN for realizing a tunable piezotronic effect. Such a mechanism uses interface polar symmetry and shielding of bulk piezo-charges to drive an electrical switching between high- and low-strain sensitivity states. The tunability is preserved across different indenter sizes, while spherical tips with larger radii further enhance the modulation and tuning range due to strain-gradient size effects. Our piezotronic device has a wide sensitivity tunability window of 24 403, a large pressure sensitivity of 223.2 meV·MPa^-1, and ultrahigh strain sensitivity of 1.43 × 10⁸. Moreover, the piezotronic device shows exceptional mechanical durability up to 10 000 loading cycles and preserves electrical tunability even under dynamic operation. This study enriches piezotronic physics by uncovering the cooperative roles of bulk polarization and interface symmetry in transport modulation, and establishes a viable strategy for continuous and wide-range performance tunability in a single mechanical sensor.