This study demonstrates the importance of electronic contacts in obtaining low hysteresis in Pb(Mg0.33Nb0.67)O3–PbTiO3 (PMN-PT) based thin-film ferroelectric/piezoelectric devices. Our results show that the electronic contact significantly affects both the polarization and displacement responses: capacitors with a PMN-PT layer directly in contact with a metallic La-doped BaSnO3 (LBSO) electrode layer exhibit strong hysteresis. In contrast, nearly ideal relaxor ferroelectric responses with significantly reduced hysteresis were observed for capacitors with an ultrathin metallic SrRuO3 layer between the LBSO and the PMN-PT. To explain the observed hysteresis differences, we employed a phenomenological model that assumed the presence of a dielectric layer at the LBSO/PMN-PT interface. This model qualitatively describes the measured polarization loops and attributes the increased hysteresis to processes of charge exchange across the interfacial dielectric layer. We speculate that the dielectric layer is primarily due to the initial growth layer of the PMN-PT film rather than to extended screening in the LBSO layer, as the thickness of the interfacial dielectric layer as derived from the model differs significantly from the Thomas–Fermi screening length of LBSO. Furthermore, we present band diagrams to provide qualitative insight into how charge exchange across the interfacial dielectric layer impacts the band structure and hysteresis of the PMN-PT heterostructure.
We characterize a 20-μm-thick bimorph X-cut lithium niobate (LN) piezoelectric micromachined ultrasonic transducer from room temperature to 1000 °C using an open-air measurement platform built around a fully packaged device—gold wire bonds on a ceramic printed circuit board. The platform sustains continuous operation at 800 °C, confirmed by frequency-response measurements at the start and end of a 1-h dwell. A sodium-silicate bondline that fills coefficient-of-thermal-expansion-driven substrate cracks as they form is central to sustained operation above 500 °C. The flexural resonance shifts downward with increasing temperature up to the onset of substrate cracking, and a coherent simple-harmonic-oscillator/modified Butterworth–Van Dyke fit extracts a temperature-dependent effective stiffness for LN up to ∼400 °C; above the 500–600 °C cracking onset, the resonance evolves non-monotonically as crack formation and bondline stabilization successively modify the modal boundary conditions. The measurement terminates near 1000 °C as the gold electrodes dewet and diffuse approaching their melting point (∼1064 °C), rather than at any LN material limit, indicating that packaging and metallization—not the piezoelectric film—set the practical ceiling for these devices. The platform is reusable for high-operating-temperature microelectromechanical systems beyond this device.
Biomedical electronic devices are developed to monitor physiological activity and deliver interventions at specific sites in the body. Their operation requires stable biological interfaces, suitable power delivery and reliable interpretation of electrical signals. These requirements become particularly important during movement and prolonged use, when changes in the interface can affect device performance. Developing clinically useful systems therefore requires an understanding of how materials and device architectures preserve the intended function under these conditions. Recent contributions to APL Electronic Devices address these requirements through advances in wearable sensors, biomolecular detection, soft actuators and power sources. We argue that the next stage of development requires closer integration of these capabilities around defined clinical needs. This Editorial examines the resulting design priorities for biological interfaces, feedback control, functional lifetime and reproducible fabrication.
In this letter, a plasma-assisted molecular beam epitaxy-grown N-polar Al0.55Ga0.45N channel high-electron-mobility transistor was demonstrated to exhibit stable DC and RF performance at elevated temperatures. At 300 °C, the device showed improved electrical characteristics, including a channel contact resistance of 246 Ω mm, a maximum drain current of 37.4 mA/mm, and a transconductance of 4.7 mS/mm, while maintaining a stable threshold voltage of −5.4 V. Consequently, enhanced RF performance was achieved compared to room temperature, with the cutoff frequency (fT) and maximum oscillation frequency (fmax) increasing to 0.62 and 1.19 GHz, respectively, at 300 °C.
We demonstrate high-temperature operation of Al0.83In0.17N/GaN high-electron-mobility transistors (HEMTs) at 800 K (∼527 °C) enabled by a post-fabrication supercritical fluid (SCF) treatment. NH3-based SCF (NH3-SCF) and O2-based SCF (O2-SCF) processes are systematically compared, showing that O2-SCF provides more effective oxidative passivation for interface engineering under extreme-temperature conditions. The O2-SCF treatment suppresses off-state leakage current by more than five orders of magnitude at room temperature and over two orders at 800 K, while increasing on-current by 30%–40% and reducing on-resistance from 10 to 8 Ω mm. The O2-SCF devices exhibit a subthreshold swing of 64 mV/dec and an on/off current ratio of 1012 at room temperature, retaining 230 mV/dec and 104 at 800 K, among the best reported for III-nitride HEMTs operating above 500 °C. These results demonstrate that O2-SCF is an effective post-fabrication strategy for improving interface quality and mitigating performance degradation at elevated temperatures in Al0.83In0.17N/GaN HEMTs, with potential for electronics in harsh environments.
