Flexible self-powered piezoelectric pressure sensor based on GaN/p-GaN coaxial nanowires

Abstract The development of flexible, highly sensitive, and durable pressure sensor, measuring dynamic and static pressure signals, and having the self-power generation property is a prime need. Here we propose the flexible piezoelectric pressure sensor (PEPS) based on p-n junction coaxial GaN nanowires (NWs). The self-powered PEPS demonstrates a high-power density of 66.3 µW/cm2 at an optimum load resistance of 6 MΩ. Additionally, it stores an electrical energy of 53.8 µJ for a normally oriented pressure pulse of 2.0 kPa, calculated from the resultant current and voltage signals. The energy-harvesting capability of the self-powered PEPS is also demonstrated by charging a capacitor. The pressure sensors based on semiconductor piezoelectric materials lack the ability of measuring static signals because of presence of excess free carriers. The proposed PEPS demonstrates the stable voltage response to both dynamic and static pressure because internal screening was suppressed greatly by p-n junction atop of coaxial NWs and by high resistivity of p-GaN shell. A voltage-decay time constant of 19,150 s is exhibited, which is a great advancement for semiconductor-based PEPSs. Additionally, it exhibits a linear response (R2 = 0.992), a high sensitivity (14.25 V/kPa), a fast response time (55 ms), and the long-term durability.