简介：象和局部剪切带逐渐明显(图2和5)，峰值应力以及相应轴向应变则不断减小(图8和9)；3.在大于2MPa的高压固结不排水试验中，其孔隙水压/轴向应变曲线明显不同于常压(图3)；4.上述与压力相关的力学性质均与黏土微观结构相关(图6和12)；5.高压下黏土难以达到所谓的临界状态。

简介：Thedegradationmechanismofenhancement-modeAlGaN/GaNhighelectronmobilitytransistors(HEMTs)fabricatedbyfluorineplasmaionimplantationtechnologyisonemajorconcernofHEMT’sreliability.Itisobservedthatthethresholdvoltageshowsasignificantnegativeshiftduringthetypicallong-termon-stategateoverdrivestress.Thedegradationdoesnotoriginatefromthepresenceofas-growntrapsintheAlGaNbarrierlayerorthegeneratedtrapsduringfluorineionimplantationprocess.Bycomparingtherelationshipsbetweentheshiftofthresholdvoltageandthecumulativeinjectedelectronsunderdifferentstressconditions,agoodagreementisobserved.Itprovidesdirectexperimentalevidencetosupporttheimpactionizationphysicalmodel,inwhichthedegradationofE-modeHEMTsundergateoverdrivestresscanbeexplainedbytheionizationoffluorineionsintheAlGaNbarrierlayerbyelectronsinjectedfrom2DEGchannel.Furthermore,ourresultsshowthattherearefewnewtrapsgeneratedintheAlGaNbarrierlayerduringthegateoverdrivestress,andtheionizedfluorineionscannotrecapturetheelectrons.