Step-stress experiments are performed in this paper to investigate the degradation mechanism of an AIGaN/GaN high electron mobility transistor （HEMT）. It is found that the stress current shows a recoverable decrease...Step-stress experiments are performed in this paper to investigate the degradation mechanism of an AIGaN/GaN high electron mobility transistor （HEMT）. It is found that the stress current shows a recoverable decrease during each voltage step and there is a critical voltage beyond which the stress current starts to increase sharply in our experiments. We postulate that defects may be randomly induced within the A1GaN barrier by the high electric field during each voltage step. But once the critical voltage is reached, the trap concentration will increase sharply due to the inverse piezoelectric effect. A leakage path may be introduced by excessive defect, and this may result in the permanent degradation of the A1GaN/GaN HEMT.展开更多
This paper focuses on the issue of reliability and global sensitivity analysis for an airplane slat mechanism considering the uncertainties in the wear process of mechanical components.First,the multi-body kinematic m...This paper focuses on the issue of reliability and global sensitivity analysis for an airplane slat mechanism considering the uncertainties in the wear process of mechanical components.First,the multi-body kinematic model of the slat mechanism is built in the ADAMS software.The geometrical sizes of the roller wheels after wear degradation are considered as input variables and the angle the slat should turn is considered as the output response.To accurately identify the influential roller wheels to the reliability and robustness of the slat mechanism,the failure probability based sensitivity and variance-based sensitivity indices are introduced.Comprehensive analysis of the results have shown that the reliability analysis and global sensitivity theory can help engineers find significant parts by their contributions,thus provide guidance for mechanical design and maintenance.展开更多
In spite of their extraordinary performance, AlGaN/GaN high electron mobility transistors （HEMTs） still lack solid reliability. Devices under accelerated DC stress tests （off-state, VDS = 0 state, and on-state step...In spite of their extraordinary performance, AlGaN/GaN high electron mobility transistors （HEMTs） still lack solid reliability. Devices under accelerated DC stress tests （off-state, VDS = 0 state, and on-state step-stress） are investigated to help us identify the degradation mechanisms of the AlGaN/GaN HEMTs. All our findings are consistent with the degradation mechanism based on crystallographic-defect formation due to the inverse piezoelectric effects in Ref. [1] （Joh J and del Alamo J A 2006 IEEE IDEM Tech. Digest p. 415）. However, under the on-state condition, the devices are suffering from both inverse piezoelectric effects and hot electron effects, and so to improve the reliability of the devices both effects should be taken into consideration.展开更多
In this paper, we have discussed the effect of electrical stress on GaN light emitting diode （LED）. With the lapse of time, the LED with an applied large current stress can reduce its current more than without such ...In this paper, we have discussed the effect of electrical stress on GaN light emitting diode （LED）. With the lapse of time, the LED with an applied large current stress can reduce its current more than without such a stress under a large forward-voltage drop. Its scanning electron microscopy （SEM） image shows that there exist several pits on the surface of the p-metal. With an electrical stress applied, the number of pits greatly increases. We also find that the degradation of GaN LED is related to the oxidized Ni/Au ohmic contact to p-GaN. The electrical activation of H-passivated Mg acceptors is described in detail. Annealing is performed in ambient air for 10 min and the differential resistances at a forward-voltage drop of 5 V are taken to evaluate the activation of the Mg acceptors. These results suggest some mechanisms of degradation responsible for these phenomena, which are described in the paper.展开更多
基金Project supported by the Program for New Century Excellent Talents in University (Grant No.NCET-12-0915)
文摘Step-stress experiments are performed in this paper to investigate the degradation mechanism of an AIGaN/GaN high electron mobility transistor （HEMT）. It is found that the stress current shows a recoverable decrease during each voltage step and there is a critical voltage beyond which the stress current starts to increase sharply in our experiments. We postulate that defects may be randomly induced within the A1GaN barrier by the high electric field during each voltage step. But once the critical voltage is reached, the trap concentration will increase sharply due to the inverse piezoelectric effect. A leakage path may be introduced by excessive defect, and this may result in the permanent degradation of the A1GaN/GaN HEMT.
基金supported by the National Natural Science Foundation of China(NSFC51975476)the Natural Science Basic Research Plan in Shaanxi Province(2020JM-135)Aerospace Science and Technology Foundation of China。
文摘This paper focuses on the issue of reliability and global sensitivity analysis for an airplane slat mechanism considering the uncertainties in the wear process of mechanical components.First,the multi-body kinematic model of the slat mechanism is built in the ADAMS software.The geometrical sizes of the roller wheels after wear degradation are considered as input variables and the angle the slat should turn is considered as the output response.To accurately identify the influential roller wheels to the reliability and robustness of the slat mechanism,the failure probability based sensitivity and variance-based sensitivity indices are introduced.Comprehensive analysis of the results have shown that the reliability analysis and global sensitivity theory can help engineers find significant parts by their contributions,thus provide guidance for mechanical design and maintenance.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CBA00600)the National Natural Science Foundation of China (Grant No. 61106106)the Fundamental Research Funds for the Central Universities (Grant No. K50510250006)
文摘In spite of their extraordinary performance, AlGaN/GaN high electron mobility transistors （HEMTs） still lack solid reliability. Devices under accelerated DC stress tests （off-state, VDS = 0 state, and on-state step-stress） are investigated to help us identify the degradation mechanisms of the AlGaN/GaN HEMTs. All our findings are consistent with the degradation mechanism based on crystallographic-defect formation due to the inverse piezoelectric effects in Ref. [1] （Joh J and del Alamo J A 2006 IEEE IDEM Tech. Digest p. 415）. However, under the on-state condition, the devices are suffering from both inverse piezoelectric effects and hot electron effects, and so to improve the reliability of the devices both effects should be taken into consideration.
基金supported by the National High Technology Development Program of China (Grant No 2006AA03A108)
文摘In this paper, we have discussed the effect of electrical stress on GaN light emitting diode （LED）. With the lapse of time, the LED with an applied large current stress can reduce its current more than without such a stress under a large forward-voltage drop. Its scanning electron microscopy （SEM） image shows that there exist several pits on the surface of the p-metal. With an electrical stress applied, the number of pits greatly increases. We also find that the degradation of GaN LED is related to the oxidized Ni/Au ohmic contact to p-GaN. The electrical activation of H-passivated Mg acceptors is described in detail. Annealing is performed in ambient air for 10 min and the differential resistances at a forward-voltage drop of 5 V are taken to evaluate the activation of the Mg acceptors. These results suggest some mechanisms of degradation responsible for these phenomena, which are described in the paper.
