Bidirectional threshold voltage shift and gate leakage in 650 V p-GaN AlGaN/GaN HEMTs: The role of electron-trapping and hole-injection

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

“…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]. For Schottky gate GaN HEMTs, electron trapping at the interface yields a net negative charge in the p-GaN layer thereby resulting in a positive VTH shift since more voltage is required to create the 2DEG.…”

“…The magnitude of the VTH shift depends on the magnitude of trapped electrons. However, as the VGS stress is increased, the VTH shift changes from positive to negative due to hole trapping and accumulation at the GaN/AlGaN interface [21]. At higher VGS bias, the PiN diode in the gate stack becomes forward biased with hole injection from the p-GaN gate into the AlGaN layer and electron injection in the reverse direction.…”

Stability and Reliability of Lateral GaN Power Field-Effect Transistors

“…1) Injection of electrons from the 2DEG into the AlGaN barrier where they get trapped causing a positive V T shift [136]. This process exhibits weak thermal activation (E a = 0.17 eV in [135], reflecting the location of the traps in the AlGaN with respect to the GaN conduction band edge), and it is recoverable [137].…”

Demonstration of Electron/Hole Injections in the Gate of $p$-GaN/AlGaN/GaN Power Transistors and Their Effect on Device Dynamic Performance

“…In recent years, the p-GaN gate related reliability issues are attracting more research interest and many studies have been performed on this topic. Among these reliability issues, the device performances such as the threshold voltage (VTH) shift [4]- [10] and leakage current increase [11], [12] have attracted the most attention. The p-GaN/AlGaN/GaN heterostructure is a direct-bandgap hetero-PIN junction, in which the electron and hole injection processes are normal.…”