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Current Scaling and Electron Heating in a GaN/AlGaN Two-Dimensional Electron System
Kuang Yao Chen,Li-Hung Lin,Chin-An Chang,Chi-Te Liang,N. C. Chen,P. H. Chang,Wen-Jang Shiue,Zhi-Hao Sun 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.6
A GaN/AlGaN two-dimensional electron system (2DES) has been prepared on a Si substrate, and the electron heating effect in the 2DES has been studied experimentally by using the resistance of the 2DES as a self-thermometer. The relation $T_e$ $\sim$ $I^{1.42}$ was obtained, which is in contrast to $T_e$ $\sim$ $I^{0.5}$ in the spin-split resistivity peaks in a GaAs/AlGaAs 2DES. A possible reason for this is discussed
Enhanced Phase Relaxation in a Hybrid Ferromagnet/Semiconductor System
Kuang Yao Chen,Chun-Kai Yang,N. Aoki,Y. Ochiai,Y. Ujiie,K. A. Cheng,Li-Hung Lin,C. F. Huang,Yu-Ru Li,Yen Shung Tseng,Po-Tsun Lin,Jau-Yang Wu,Sheng-Di Lin,C.-T. Liang 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1
Hybrid ferromagnet/semiconductor systems have been the focus of considerable attention because of the transport properties of two-dimensional electron systems and their potential applications to magnetic storage and sensing devices. We use the weak localization effect to probe the dephasing mechanism at low temperatures. In our study, the zero-temperature phase-relaxation rate can be enhanced in a hybrid ferromagnet/semiconductor system, which may be due to the inhomogeneous magnetic field emanating from the Ni film. The result may improve understanding of the issue of zero-temperature dephasing in disordered systems. Hybrid ferromagnet/semiconductor systems have been the focus of considerable attention because of the transport properties of two-dimensional electron systems and their potential applications to magnetic storage and sensing devices. We use the weak localization effect to probe the dephasing mechanism at low temperatures. In our study, the zero-temperature phase-relaxation rate can be enhanced in a hybrid ferromagnet/semiconductor system, which may be due to the inhomogeneous magnetic field emanating from the Ni film. The result may improve understanding of the issue of zero-temperature dephasing in disordered systems.
Probing Insulator-quantum Hall Transitions by Current Heating
Kuang Yao Chen,N. Aoki,Y. Ochiai,K. A. Cheng,Li-Hung Lin,C. F. Huang,Yu-Ru Li,Yen Shung Tseng,Chun-Kai Yang,Po-Tsun Lin,Jau-Yang Wu,Sheng-Di Lin,C.-T. Liang 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1
We report a magneto-transport study on the two-dimensional electron system (2DES) in an Al- GaAs/GaAs heterostructure. The direct insulator to quantum Hall conductor transition is observed at low temperatures by increasing the magnetic field B perpendicular to the 2DES. We can also observe the transition by varying the current I and find a relation Te~Ia between electron effective temperature Te and current. Here, a denotes the exponent for the power law. The exponent a, however, can have different values on the two sides of the transition point, which indicates different inelastic scattering mechanisms in the low-field insulator and in the quantum Hall conductor. We report a magneto-transport study on the two-dimensional electron system (2DES) in an Al- GaAs/GaAs heterostructure. The direct insulator to quantum Hall conductor transition is observed at low temperatures by increasing the magnetic field B perpendicular to the 2DES. We can also observe the transition by varying the current I and find a relation Te~Ia between electron effective temperature Te and current. Here, a denotes the exponent for the power law. The exponent a, however, can have different values on the two sides of the transition point, which indicates different inelastic scattering mechanisms in the low-field insulator and in the quantum Hall conductor.
Electrical Measurements of an AlGaN/GaN High-electron-mobility Transistor Structure Grown on Si
Zhi-Yao Zhang,Shun-Tsung Lo,Li-Hung Lin,Kuang Yao Chen,J. Z. Huang,Zhi-Hao Sun,C.-T. Liang,N. C. Chen,Chin-An Chang,P. H. Chang 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.9
We report on magnetotransport results for an Al<sub>0.15</sub>Ga<sub>0.85</sub>N/GaN high-electron-mobility-transistor structure grown on a p-type Si (111) substrate. Our results show that there exists an approximately temperature (<i>T</i>)-independent point, which could be ascribed to a direct transition from a weak insulator to a high Landau level filling factor quantum Hall state, exists in the longitudinal resistivity ρ<sub>xx</sub>. The Hall resistivity decreases with increasing <i>T</i>, compelling experimental evidence for electron-electron interaction effects in a weakly-disordered two-dimensional (2D) system. We find that electron-electron interaction effects can be estimated and eliminated, giving rise to a corrected nominally temperature-independent Hall slope. By fitting the low-field magnetotransport data to conventional 2D weak localization theory, we find that the dephasing rate 1/τ<sub>φ</sub> is proportional to <i>T</i>. Moreover, 1/τ<sub>φ</sub> is finite as <i>T</i> → 0, evidence for zero-temperature dephasing in our system.
E.S Kannan,Gil Ho Kim,D. H. Youn,Chi-Te Liang,Jing-Han Chen,Jyun-Ying Lin,Kuang Yao Chen,Kwang-Yong Kang,Li-Hung Lin,N.C. Chen,Zhi-Yao Zhang 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.6
We report comparative magnetoresistance measurements of the two-dimensional electron gas formed in two different GaN/AlGaN quantum well structures with different starting disorder. The longitudinal magnetoresistance measurements for both the samples exhibited temperature-independent crossing points, evidence for a weak insulator - quantum Hall transition. Our data suggest that the onset of Landau quantization does not correspond to the crossing point. Moreover, the effect of the electron-electron interaction must be taken into account because the Hall resistivity shows a strong temperature dependence in the more disordered sample. Our experimental results, therefore, urge further studies on the low-field weak insulator - quantum Hall transition
Ya-Ru Liang,Mei-Chen Yang,Yao-Kuang Wu,I-Shiang Tzeng,Pei-Yi Wu,Shiang-Yu Huang,Chou-Chin Lan,Chin-Pyng Wu 한국간호과학회 2020 Asian Nursing Research Vol.14 No.1
Purpose: Some patients with respiratory failure fail initial weaning attempts and need prolonged mechanical ventilation (MV). Prolonged MV is associated with many complications and consumption of heathcare resources. Objective weaning indices help staffs to identify high-potential patients for weaning from the MV. Traditional weaning indices are not reliable in clinical practice. Transitional percentage of minute volume (TMV%) is a new index of the work of breathing. This study aimed to investigate the utility of TMV% in the prediction of weaning potential. Methods: This study was prospectively performed including all patients with prolonged MV. Researchers recorded their demographics, TMV%, respiratory parameters, Acute Physiology and Chronic Health Evaluation II score, and laboratory data upon arrival at the respiratory care center. The factors associated with successful weaning were analyzed. Results: Out of the 120 patients included, 84 (70.0%) were successfully weaned from MV. Traditional weaning indices such as rapid shallow breathing index could not predict the weaning outcome. TMV% was a valuable parameter as patients with a lower TMV%, higher tidal volume, higher hemoglobin, lower blood urea nitrogen, and lower Acute Physiology and Chronic Health Evaluation II scores had a higher rate of successful weaning. TMV%, tidal volume, and HCO3- levels were independent predictors of successful weaning, and the area under the curve was .79 in the logistic regression model. Conclusion: TMV% is a novel and effective predictor of successful weaning. Patients with lower TMV% had a higher MV weaning outcome. Once patients with a high potential for successful weaning are identified, they should be aggressively weaned from MV as soon as possible.
Jian-Zhe Huang,Li-Hung Lin,Chin-An Chang,Chi-Te Liang,Kuang Yao Chen,Kui-Ming Chen,N. C. Chen,P. H. Chang,Shiou-Shian Han,Zhi-Hao Sun 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.3
We report on experimental studies of an Al$_{0.15}$Ga$_{0.85}$N/GaN high-electron-mobility transistor structure grown on a $p$-type Si (111) substrate. This structure is compatible with complementary metal-oxide-semiconductor (CMOS) technology and, thus, has great potential device applications. The low-temperature magnetoresistivity shows a parabolic dependence on the applied perpendicular magnetic field. This effect is ascribed to electron-electron interaction (EEI) effects in a weakly-disordered two-dimensional system. Our experimental results agree with the EEI theory when the correction term in the ballistic region has been subtracted.
Su Vincent Yi-Fong,Ko Szu-Wen,Chang Yuh-Lih,Chou Yueh-Ching,Lee Hsin-Chen,Yang Kuang-Yao,Chou Kun-Ta,Hsu Chia-Chen 대한천식알레르기학회 2022 Allergy, Asthma & Immunology Research Vol.14 No.3
Purpose: Current clinical guidelines are unclear regarding the association of cardiovascular medication with the risk of acute exacerbation (AE) in patients with asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO). Methods: We conducted a retrospective cohort study by interrogating the claims database of Taipei Veterans General Hospital. Patients with coexistent fixed airflow limitation and asthma were enrolled as an ACO cohort between 2009 and 2017. Exposure to cardiovascular medications, including angiotensin converting enzyme inhibitors (ACEIs), angiotensin II receptor blockers (ARBs), non-selective beta-blockers, cardioselective beta-blockers, dihydropyridine (DHP) calcium channel blockers (CCBs), and non-DHP CCBs, in 3-month period each served as time-dependent covariates. Patients receiving a cardiovascular medication ≥ 28 cumulative daily doses were defined as respective cardiovascular medication users. Patients were followed up until December 31, 2018. The primary endpoint was severe AE, defined as hospitalization or emergency department visit for either asthma, COPD, or respiratory failure. The secondary outcome was moderate AE. Results: The final study cohort consisted of 582 ACO subjects, with a mean follow-up period of 2.98 years. After adjustment, ARB (hazard ratio [HR], 0.64, 95% confidence interval [CI], 0.44–0.93, P = 0.019), cardioselective beta-blocker (HR, 0.29, 95% CI, 0.11–0.72, P = 0.008) and DHP CCB (HR, 0.66, 95% CI, 0.45–0.97, P = 0.035) therapies were associated with lower risks of severe AE. ARB (HR, 0.42, 95% CI, 0.30–0.62, P < 0.001) and DHP CCB (HR, 0.55, 95% CI, 0.38–0.80, P = 0.002) therapies were associated with lower risks of moderate AE. Cardioselective beta-blockers, ARBs, and DHP CCBs were associated with lower risks of severe AE in frequent exacerbators. ACEI, non-selective beta-blocker, or non-DHP CCB use did not change the risk of severe AE. Conclusions: ARB, cardioselective beta-blocker, and DHP CCB therapies may lower the risk of AE in patients with ACO.