Interface and oxide trap states of SiO2/GaN metal–oxide–semiconductor capacitors and their effects on electrical properties evaluated by deep level transient spectroscopy

The relationship between the electrical properties and the carrier trap properties of the SiO2/GaN metal–oxide–semiconductor (MOS) capacitors was investigated using electrical measurements and deep level transient spectroscopy (DLTS). The capacitance–voltage (C–V) measurement showed that the frequency dispersion of the C–V curves became smaller after an 800 °C annealing in O2 ambient. DLTS revealed that before the annealing, the interface trap states, in a broad energy range above the midgap of GaN, were detected with the higher interface state density at around 0.3 and 0.9 eV below the conduction band minimum (Ec) of GaN. Moreover, the oxide trap states were formed at around 0.1 eV below the Ec of GaN, plausibly indicating a slow electron trap with a tunneling process. Although both trap states affect the electrical reliability and insulating property of the SiO2/GaN MOS capacitors, they were found to drastically decrease after the annealing, leading to the improvement of the electrical properties.Shingo Ogawa, Hidetoshi Mizobata, Takuma Kobayashi, Takayoshi Shimura, Heiji Watanabe; Interface and oxide trap states of SiO2/GaN metal–oxide–semiconductor capacitors and their effects on electrical properties evaluated by deep level transient spectroscopy. J. Appl. Phys. 7 September 2023; 134 (9): 095704. https://doi.org/10.1063/5.016589

Ventricular Fibrillation in Patient with Multi-vessel Coronary Spasm Four Days after the Initiation of Oral Beta-blocker

We describe a case of ventricular fibrillation occurring in a patient with multi-vessel coronary spasm after the initiation of an oral beta-blocker. A 56-year-old man began to experience chest discomfort and his computed tomography revealed intermediate coronary stenoses. He was administered medications including an oral beta-blocker but suddenly collapsed while walking 4 days later. An automated external defibrillator detected ventricular fibrillation and delivered successful electrical cardioversion. An acetylcholine provocation test after stabilization of the status revealed triple-vessel coronary spasm. Beta-blockers may provoke exacerbation of coronary spasm and result in lethal arrhythmia

Passivation of hole traps in SiO₂/GaN metal-oxide-semiconductor devices by high-density magnesium doping

A major challenge in GaN-based metal-oxide-semiconductor (MOS) devices is significant hole trapping near the oxide/GaN interface. In this study, we show that the density and energy level of the hole traps depends crucially on the concentration of magnesium (Mg) dopants in GaN layers. Although the surface potential of a conventional SiO₂/p-GaN MOS device is severely pinned by hole trapping, hole accumulation and very low interface state densities below 1011 cm−2 eV−1 are demonstrated for MOS capacitors on heavily Mg-doped GaN epilayers regardless of the degree of dopant activation. These findings indicate the decisive role of Mg atoms in defect passivation.This is the Accepted Manuscript version of an article accepted for publication in Applied Physics Express. IOP Publishing Ltd are not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.35848/1882-0786/acfc95

Reduction of interface and oxide traps in SiO₂/GaN MOS structures by oxygen and forming gas annealing

The effect of post-deposition annealing on the electrical characteristics of SiO₂/GaN MOS devices was investigated. While the key to the improvement was using oxygen annealing to form an interfacial GaOx layer and forming gas annealing to passivate the remaining defects, caution must be taken not to produce a fixed charge through reduction of the GaOx layer. By growing the GaOx layer with oxygen annealing at 800 ℃ and performing forming gas annealing at a low temperature of 200 ℃, it became possible to suppress the reduction of GaOx and to reduce the interface traps, oxide traps, and fixed charge simultaneously.This is the Accepted Manuscript version of an article accepted for publication in Applied Physics Express. IOP Publishing Ltd are not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.35848/1882-0786/acc1bd

Formation of high-quality SiO₂/GaN interfaces with suppressed Ga-oxide interlayer via sputter deposition of SiO₂

While the formation of a GaOx interlayer is key to achieving SiO₂/GaN interfaces with low defect density, positive fixed charge is rather easily generated through the reduction of GaOx layer if the annealing conditions are not properly designed. In this study, we minimized the unstable GaOx layer by sputter SiO₂ deposition. Negligible GaOx growth was confirmed by synchrotron radiation X-ray photoelectron spectroscopy, even when post-deposition oxygen annealing up to 600℃ was performed. A MOS device with negligible capacitance–voltage hysteresis, stable flat-band voltage, and low leakage current was demonstrated by performing oxygen and forming gas annealing at temperatures of 600℃ and 400℃, respectively.This is the Accepted Manuscript version of an article accepted for publication in Japanese Journal of Applied Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.35848/1347-4065/acd1ca

A case of hepatocellular adenoma with pedunculated development and difficulty in diagnosis

Hepatocellular adenoma (HCA) is a benign hepatocyte-derived epithelial tumor. HCA is associated with oral contraceptive use among Caucasian populations. We report a case of hepatocellular adenoma with a pedunculated protuberance and high protein induced by vitamin K absence or antagonist-II (PIVKA-II) levels, which made diagnosis challenging. The patient was a 22-year-old woman. In a medical check-up, a high γ-GTP level was detected and a 115-mm solid mass was found in her lower abdomen via abdominal ultrasonography. A blood test showed a high PIVKA-II level. Abdominal CT showed a tumor in the lower abdomen. Contrast-enhanced CT showed a blood vessel thought to be the left hepatic artery connecting to the mass, and a blood vessel thought to be the left hepatic vein returning from the mass to the inferior vena cava. In EOB-MRI, uneven enhancement was observed after contrast imaging, but washout in the equilibrium phase was unclear. Parenchymal hepatocyte phases showed a pale, non-uniform, high signal. These findings indicated that the tumor was derived from the left lobe of the liver and was suggestive of HCC. Surgical resection was then performed. A pathological examination led to a diagnosis of HCA, corresponding to unclassified HCA. The WHO classification of tumors of the digestive system based on an immunohistological examination includes HNF1α-inactivated HCA, β-catenin-activated HCA, inflammatory HCA, and unclassified HCA. In summary, our patient had a large HCA with pedunculated protrusion into the extrahepatic pelvic cavity. This case was challenging to diagnose because of abnormally high PIVKA-II levels, and it was resected laparoscopically

Renal effects of sodium glucose co-transporter 2 inhibitors in Japanese type 2 diabetes mellitus patients with home blood pressure monitoring

Decrease in blood pressure contributes to the reno-protective effects of sodium-glucose cotransporter 2 inhibitors; however, its relationship with home monitoring of blood pressure is unclear. We retrospectively analyzed 101 visiting members of the Kanagawa Physicians Association with type 2 diabetes mellitus and chronic kidney disease who were taking sodium-glucose cotransporter 2 inhibitors and who monitored blood pressure at home for a median treatment period of 14 months. At baseline, the mean value of HbA1c was 59.3 mmol/mol (7.6%) and the median value of albumin-creatinine ratio was 30.9 mg/gCr that was evaluated in 88 patients. The mean blood pressure both at office and home significantly decreased, and there was a significant positive correlation between the change in albumin–creatinine ratio and both blood pressures. Controlled hypertension, masked hypertension, white coat hypertension, and sustained hypertension were observed in 10.9%, 13.9%, 12.9%, and 62.4% of patients at the initiation of therapy, which changed to 10.9%, 16.8%, 17.8%, and 54.5% at the time of the survey, respectively. In conclusion, management of blood pressure both at office and home was found to be important for the reno-protective effects of sodium-glucose cotransporter 2 inhibitors along with strict blood pressure management