Threshold Voltage Instability Mechanisms in p-GaN Gate AlGaN/GaN HEMTs

Characterizing Threshold Voltage Shifts and Recovery in Schottky Gate and Ohmic Gate GaN HEMTs

“…Considering the 3 V gate stress in Fig. 7(a), the Schottky Gate GaN HEMT exhibits a positive threshold voltage shift, which is in agreement with [18]. This positive VTH shift is caused by trapping of electrons in the AlGaN/GaN interface [18].…”

“…7(a), the Schottky Gate GaN HEMT exhibits a positive threshold voltage shift, which is in agreement with [18]. This positive VTH shift is caused by trapping of electrons in the AlGaN/GaN interface [18]. For the stress durations evaluated (1s to 100 s) there is no significant impact of the stress time on the threshold voltage shift, which is around +5%.…”

“…In this case the peak shift is now negative (-3.6%), followed by a fast dip, with a further reduction to -14.7%, and a slow recovery transient to the pre-stress value. In [18] the authors reported similar characteristics for medium gate voltage stresses, identifying three different mechanisms responsible of the different VTH shifts: electron trapping at the AlGaN/GaN interface, hole trapping in the AlGaN barrier and hole depletion. Fig.…”

“…Commercially available GaN HEMTs have been the subject of different studies including electrothermal characterization [5][6][7]and reliability studies (summarized in [8]), with a JEDEC committee (JC-70) focused on the development of standards for GaN power devices [9,10]. The reliability studies include power cycling [11][12][13], dynamic ON-state resistance [14][15][16] and threshold voltage (VTH) instability [17][18][19][20][21][22][23], which is the focus of the investigations presented in this paper.…”

“…The previous studies [17][18][19][20][21][22][23] highlight the complexity of the gate stack structure and different threshold voltage shifts depending on the magnitude of the gate stress voltage. For example, in Schottky gate GaN devices, positive VTH drift at low gate voltage VGS bias has been reported due to electron trapping in acceptor like states at the AlGaN/GaN interface [21,24].…”