The effect of hydrogen on defects in AlGaN/GaN high-electron-mobility transistors (HEMTs) was investigated by using low-frequency noise (LFN) method. The results show that drain-to-source current of AlGaN/GaN HEMTs after hydrogen treatment is significantly larger than that of the fresh AlGaN/GaN HEMTs. The maximum variation of drain-to-source current is up to 80 mA at the gate-to-source voltage of 0 V and drain-to-source voltage of 5 V. The suppression of current collapse was also observed, and the gate-lag characteristic becomes better for the AlGaN/GaN HEMTs after hydrogen treatment. Extracted by the LFN method, the trap density decreases by about one order of magnitude in the AlGaN/GaN HEMTs after hydrogen treatment, and this would lead to less depleted electrons in the channel 2-D electron gas. The mechanism for the reduction of trap density could be attributed to H-passivated defects at AlGaN surface, AlGaN barrier layer, and heterostructure interface. The results of this paper may be useful in the design and application of AlGaN/GaN HEMTs.

The degradation behavior and its mechanisms of E-mode GaN high electron mobility transistors (HEMTs) with p-GaN gate under electrostatic discharge (ESD) stress were investigated. Reverse short-pulse stress was generated by a transmission line pulse (TLP) tester in order to simulate the static electricity. The experiment results show that the reverse short-pulse stress leads to the characteristic degradation of the E-mode GaN HEMTs with p-GaN gate. The values of the threshold voltage and on-resistance increase, and the gate capacitance curve shifts positively. The low-frequency noises (LFNs) were obtained for the E-mode GaN HEMTs with p-GaN gate before and after the reverse short-pulse stress. The concentration of traps was extracted, and it has doubled after 700 cycles. The degradation mechanism could be attributed to the generation of traps at p-GaN/AlGaN heterointerface, AlGaN barrier, and GaN/AlGaN interface. Such an investigation can be a significant reference in the design and application of E-mode GaN power devices.

Low-frequency noise (LFN) is investigated in a set of indium-zinc-oxide thin-film transistors (IZO TFTs) with fixed channel width (W=10 μm) and different channel lengths (L=10, 20, 30 and 40 μm) from sub-threshold, linear to saturation regions. The drain current noise power spectral density is measured as a function of effective gate voltage and drain current. The variation slopes of normalized noise with effective gate voltage are in the range of -1.27 and -1.48, which are close to the prediction of the mobility fluctuation mechanism. According to the N-μ model, the flat-band voltage noise spectral density and coulomb scattering coefficient are extracted. Subsequently, variations of noise with the drain current in the above threshold region are analyzed by considering the band-gap distribution of the tail states. Finally, the BSIM model is also used to model 1/f noise in the IZO TFTs. The noise parameter NOIB is extracted which is inversely proportional to the effective gate voltage. Good agreements are achieved between the simulated and measured results in the linear region.

In this article, we experimentally investigate the degradation mechanisms of GaN high-electron mobility transistors (HEMTs) with p-type gate during long-term high-temperature reverse bias (HTRB) stress and negative bias temperature instability (NBTI) stress. Based on a number of stress/recovery experiments, we demonstrate that HTRB stress could lead to hole emission in the p-GaN layer, making threshold voltage (Vth) positively shift, while NBTI stress could result in detrapping at the AlGaN/GaN interface or the AlGaN layer and make Vth negatively shift. It is also found that the temperature rise can suppress the positive Vth shift and accelerate its recovery process in HTRB experiments.

This work investigates the degradation mechanism of 1.2 kV silicon carbide (SiC) metal oxide semiconductor field-effect transistor (MOSFET) under positive or negative long-term high-temperature gate bias (HTGB) stress. After positive long-term HTGB stress, the device shows a positive shift in threshold voltage ( ${V}_{\text {th}}{)}$ and an increase in ON-state resistance ( ${R}_{ \mathrm{\scriptscriptstyle ON}}{)}$ , which mainly results from the electron traps at or near the SiC/SiO2 interface. While subjected to negative HTGB stress, the drift of $V_{\text {th}}$ is time-dependent and correlated with the gate bias. For the device biased at a low gate voltage of −10 V, due to the hole traps at or near the interface, its ${V}_{\text {th}}$ exhibits negative shift all the time. But the drift of ${V}_{\text {th}}$ for the device biased at a higher voltage of −20 V is decreased first with the stress time, then is increased with the stress time, which may result from the hole traps and the additional electron traps introduced by the tunneling effect. Through the low-frequency noise technology, it is demonstrated that the trap density of the device biased at higher negative gate voltage of −20 V has been increased up to three times.

We have investigated the effect of hot electron stress on the electrical properties of AlGaN/GaN high electron mobility transistors (HEMTs) of hydrogen poisoning. The AlGaN/GaN HEMTs were biased at the semi-on state, and they suffered from the hot electron stress. The devices of hydrogen poisoning were degraded, while there is almost no degradation for the fresh ones. The hot electron stress leads to the significantly positive shift of threshold voltage and the notable decrease of drain-to-source current for the AlGaN/GaN HEMTs of hydrogen poisoning. For the AlGaN/GaN HEMTs of hydrogen poisoning, the trap density increases by about one order of magnitude after the hot electron stress experiment. The physical mechanism can be attributed to electrically active traps due to the dehydrogenation of passivated point defects at AlGaN surface, AlGaN barrier layer, and heterostructure interface. The results of this paper may be useful in the design and application of AlGaN/GaN HEMTs.