Piezo- and photo-voltage field-effect transistor

Photo-voltage field-effect transistor (FET), consisting of one semiconductor as conduction channel and another semiconductor as light absorber, utilizes photo-generated charges induced photo-voltage at the heterojunction interface originated from photovoltaic effect to change the conduction channel thickness and thus the conduction current. Despite of the illumination induced photo-voltage, applied strain can also produce piezoelectric polarization charges and hence a piezo-voltage at the heterojunction interface to modulate the conduction channel thickness. Here we theoretically study the basic characteristics of an n-ZnO/p-Si heterojunction FET, successfully demonstrate the modulation behaviors of FET's characteristics by both piezo-voltage and photo-voltage, and explain the physical principles that govern the piezo-voltage and photo-voltage modulation. With a tensile strain of ε = 0.15‰ or a 0.5 μW/cm² UV illumination, the saturation drain current I_Dsat of FET is enhanced by about 25%. Besides, the influences of structural parameters and doping concentrations on piezo-voltage modulation behavior are systematically studied and the guidance for piezo-voltage FET design is given. We also propose a piezo- and photo-voltage field-effect transistor by combining the piezo-voltage and photo-voltage together and illustrate the cooperation of them. Our results show that not only electric gate voltage V_GS, but also strain induced piezo-voltage and illumination induced photo-voltage, can effectively control the conduction channel thickness and current of heterojunction FET, and present the potential of piezo- and photo-voltage field-effect transistor in the fields of piezotronics and piezo-phototronics.