Piezotronics is new-branch interface engineering for efficient electromechanical coupling of semiconductor heterojunctions, with broad applications in tactile sensing, human–machine communications and tunable electronics. The piezotronic modulation is usually dominated by intrinsic inversion-asymmetry piezoelectric polarization, while the piezoelectric polarization induced by ubiquitous and field-induced structural asymmetry remains largely overlooked. Motivated by the symmetry-governed spin-orbit physics, we here reveal an entangled interface–bulk piezotronic effect in polar metal–insulator–piezoelectric semiconductor tunneling heterojunctions. The interface and electric-field-induced bulk piezotronic effects coexist and jointly modulate quantum tunneling transport and capacitance property. Depending on the polar direction of heterojunction, two piezotronic effects regulate the tunneling current either cooperatively or competitively through barrier-height modulation. External pressure and bias voltage can optimize the cooperation and competition. In addition, device capacitance shows the opposite cooperation–competition relationship because it is governed by barrier-width modulation. Therefore, cooperative current modulation is accompanied by competitive capacitance modulation, and vice versa, indicating their entangled relationship. This work establishes capacitance as an effective probe of hidden bulk piezotronic effects and provides a framework for designing interface-engineered tunneling sensors and mechanically tunable semiconductor devices.

The luminescence of semiconductor quantum dots (QDs) can be adjusted using the piezotronic effect. An external mechanical force applied on the QD generates a piezoelectric potential, which alters the luminescence of the QD. A small mechanical force may induce a significant change on the emission spectrum. In the case of InN QDs, it is demonstrated that the unforced emission wavelength is more than doubled by a force of 1 μN. The strategy of using the piezotronic effect to tune the color of the emission leads to promising noncontact forcemeasurement applications in biological and medical sensors and force-sensitive displays. Several piezoelectric semiconductor materials have been investigated in terms of the tunability of the emission wavelength in the presence of an external applied force. It is found that CdS and CdSe demonstrate much higher tunability δλ/δF, which makes them suitable for micro/nano-newton force measurement applications.

We report on manipulating the stimulated emission of monolayer molybdenum disulfide (MoS₂) with the piezoelectric effect. The analysis is based on quantum mechanics. The stimulated emission of this two-dimensional material has been simulated to establish the relation between the total emission rate and the energy of the photon excitation. We demonstrate that the piezoelectric-induced charges enhance the emission rate by changing the carrier concentration. It is found that the emission intensity is proportional to the carrier density in the low-density range, and eventually reaches a steady value in the high-density region. An externally applied mechanical force also leads to a change in the second harmonic generation of the monolayer MoS₂.