Flexible transistors are the next generation sensing technology, due to multiparametric analysis, reduced complexity, biocompatibility, lightweight with tunable optoelectronic properties. We summarize multitude of applications realized with OFETs.

The monolithic three-dimensional vertical integration of thin-film transistor (TFT) technologies could be used to create high-density, energy-efficient and low-cost integrated circuits. However, the development of scalable processes for integrating three-dimensional TFT devices is challenging. Here, we report the monolithic three-dimensional integration of indium oxide (In₂O₃) TFTs on a silicon/silicon dioxide (Si/SiO₂) substrate at room temperature. We use an approach that is compatible with complementary metal–oxide–semiconductor (CMOS) processes to stack ten n-channel In₂O₃ TFTs. Different architectures—including bottom-, top- and dual-gate TFTs—can be fabricated at different layers in the stack. Our dual-gate devices exhibit enhanced electrical performance with a maximum field-effect mobility of 15 cm² V⁻¹ s⁻¹, a subthreshold swing of 0.4 V dec⁻¹ and a current on/off ratio of 10⁸. By monolithically integrating dual-gate In₂O₃ TFTs at different locations in the stack, we created unipolar invertor circuits with a signal gain of around 50 and wide noise margins. The dual-gate devices also allow fine-tuning of the invertors to achieve symmetric voltage-transfer characteristics and optimal noise margins.

Gas sensor technology is widely utilized in various areas ranging from home security, environment and air pollution, to industrial production. It also hold great promise in non-invasive exhaled breath detection and an essential device in future internet of things. The past decade has witnessed giant advance in both fundamental research and industrial development of gas sensors, yet current efforts are being explored to achieve better selectivity, higher sensitivity and lower power consumption. The sensing layer in gas sensors have attracted dominant attention in the past research. In addition to the conventional metal oxide semiconductors, emerging nanocomposites and graphene-like two-dimensional materials also have drawn considerable research interest. This inspires us to organize this comprehensive 2020 gas sensing materials roadmap to discuss the current status, state-of-the-art progress, and present and future challenges in various materials that is potentially useful for gas sensors.

The proposed H ₂ S gas sensor is a novel heterojunction combination that can readily absorb toxic gases, changing the channel resistance of the device. The OFET device is a highly stable and selective tool that can help in taking preventive measures.

In this Letter, we report on a monolithically integrated β-Ga₂O₃ NMOS inverter integrated circuit (IC) based on heteroepitaxial enhancement mode (E-mode) β-Ga₂O₃ metal-oxide-semiconductor field-effect transistors on low-cost sapphire substrates. A gate recess technique was employed to deplete the channel for E-mode operation. The E-mode devices showed an on-off ratio of ∼10⁵ with a threshold voltage of 3 V. In comparison, control devices without the gate recess exhibited a depletion mode (D-mode) with a threshold voltage of $-$ 3.8 V. Furthermore, depletion-load NMOS inverter ICs were fabricated by monolithically integrating D- and E-mode transistors on the same substrate. These NMOS ICs demonstrated inverter logic operation with a voltage gain of 2.5 at V_DD = 9 V, comparable with recent GaN and other wide-bandgap semiconductor-based inverters. This work lays the foundation for heteroepitaxial low-cost and scalable β-Ga₂O₃ ICs for monolithic integration with (ultra)wide bandgap Ga₂O₃ power devices.