Effect of Annealing Environment on the Performance of Sol-Gel-Processed ZrO2 RRAM

We investigate the annealing environment effect on ZrO2-based resistive random-access memory (RRAM) devices. Fabricated devices exhibited conventional bipolar-switching memory properties. In particular, the vacuum-annealed ZrO2 films exhibited larger crystallinity and grain size, denser film, and a relatively small quantity of oxygen vacancies compared with the films annealed in air and N2. These led to a decrease in the leakage current and an increase in the resistance ratio of the high-resistance state (HRS)/low-resistance state (LRS) and successfully improved non-volatile memory properties, such as endurance and retention characteristics. The HRS and LRS values were found to last for 104 s without any significant degradation. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.1

Sol-gel Processed Yttrium-doped SnO2 Thin Film Transistors

Y-doped SnO2 thin film transistors were successfully fabricated by means of sol-gel process. The effect of Y concentration on the structural, chemical, and electrical properties of sol-gel-processed SnO2 films was investigated via GIXRD, SPM, and XPS; the corresponding electrical transport properties of the film were also evaluated. The dopant, Y, can successfully control the free carrier concentration by suppressing the formation of oxygen vacancy inside SnO2 semiconductors due to its lower electronegativity and SEP. With an increase of Ywt%, it was observed that the crystallinity and oxygen vacancy concentration decreased, and the operation mode of SnO2 thin film transistor changed from accumulation (normally on) to enhancement mode (normally off) with a positive Vth shift. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.1

Improved Tunneling Property of p+Si Nanomembrane/n+GaAs Heterostructures through Ultraviolet/Ozone Interface Treatment

Here, heterostructures composed of p+Si nanomembranes (NM)/n+GaAs were fabricated by ultraviolet/ozone (UV/O3, UVO) treatment, and their tunneling properties were investigated. The hydrogen (H)-terminated Si NM was bonded to the oxygen (O)-terminated GaAs substrate, leading to Si/GaAs tunnel junctions (TJs). The atomic-scale features of the H-O-terminated Si/GaAs TJ were analyzed and compared to those of Si/GaAs heterojunctions with no UVO treatment. The electrical characteristics demonstrated the emergence of negative differential resistance, with an average peak-to-valley current ratio of 3.49, which was examined based on the band-to-band tunneling and thermionic emission theories

Polarization-Charge Inversion at Al2O3/GaN Interfaces through Post-Deposition Annealing

The effects of post-deposition annealing (PDA) on the formation of polarization-charge inversion at ultrathin Al2O3/Ga-polar GaN interfaces are assessed by the analysis of energy band bending and measurement of electrical conduction. The PDA-induced positive interface charges form downward energy band bending at the Al2O3/GaN interfaces with polarization-charge inversion, which is analyzed using X-ray photoelectron spectroscopy. Net charge and interface charge densities at the Al2O3/GaN interfaces are estimated after PDA at 500 °C, 700 °C, and 900 °C. The PDA temperatures affect the formation of charge densities. That is, the charge density increases up to 700 °C and then decreases at 900 °C. Electrical characteristics of GaN Schottky diodes with ultrathin Al2O3 layers exhibit the passivation ability of the Al2O3 surface layer and the effects of polarization-charge inversion through PDA. This result can be applied to improvement in GaN-based electronic devices where surface states and process temperature work important role in device performance

Improved Tunneling Property of p+Si Nanomembrane/n+GaAs Heterostructures through Ultraviolet/Ozone Interface Treatment

Here, heterostructures composed of p+Si nanomembranes (NM)/n+GaAs were fabricated by ultraviolet/ozone (UV/O3, UVO) treatment, and their tunneling properties were investigated. The hydrogen (H)-terminated Si NM was bonded to the oxygen (O)-terminated GaAs substrate, leading to Si/GaAs tunnel junctions (TJs). The atomic-scale features of the H-O-terminated Si/GaAs TJ were analyzed and compared to those of Si/GaAs heterojunctions with no UVO treatment. The electrical characteristics demonstrated the emergence of negative differential resistance, with an average peak-to-valley current ratio of 3.49, which was examined based on the band-to-band tunneling and thermionic emission theories

Performance Optimization of Nitrogen Dioxide Gas Sensor Based on Pd-AlGaN/GaN HEMTs by Gate Bias Modulation

We investigated the sensing characteristics of NO2 gas sensors based on Pd-AlGaN/GaN high electron mobility transistors (HEMTs) at high temperatures. In this paper, we demonstrated the optimization of the sensing performance by the gate bias, which exhibited the advantage of the FET-type sensors compared to the diode-type ones. When the sensor was biased near the threshold voltage, the electron density in the channel showed a relatively larger change with a response to the gas exposure and demonstrated a significant improvement in the sensitivity. At 300 °C under 100 ppm concentration, the sensor’s sensitivities were 26.7% and 91.6%, while the response times were 32 and 9 s at VG = 0 V and VG = −1 V, respectively. The sensor demonstrated the stable repeatability regardless of the gate voltage at a high temperature