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Under reverse-bias stress (i.e., OFF-state stress with ${V} _{\text {GS}} < {V}_{\text {TH}}$) with high drain voltage, ultraviolet (UV) illumination and larger negative gate bias are found to accelerate the positive shift in threshold voltage (${V}_{\text {TH}}$) of enhancement-mode GaN MIS-FETs with fully recessed gate. These results suggest a hole-induced degradation mechanism. In the absence of UV illumination, holes could be generated by impact ionization in the high electric-field region, which is initiated by electrons injected from the source through the buffer layer. With a larger negative gate bias, more holes will flow to the gate side and pass through the silicon nitride (SiNx) gate dielectric, as SiNx does not present any energy barrier to holes. The enhanced hole transport through the dielectric under large negative gate bias could accelerate new defects generation and therefore result in the larger positive threshold voltage shifts. [ABSTRACT FROM AUTHOR]

In this paper, we carried out a systematic comparison between the enhancement-mode GaN-based fully recessed metal-insulator-semiconductor field-effect transistors (MIS-FETs) and partially recessed MIS-high-electron-mobility transistors (MIS-HEMTs) with the same gate dielectric stack (LPCVD-SiNx/PECVD-SiNx) that has delivered promising long-term reliability and stability. Despite a moderately larger on-resistance (${R}_{ \mathrm{ON}}$), the MIS-FETs deliver superior ${V}_{\text {TH}}$ uniformity and thermal stability. Under long-term gate bias stress, both the MIS-HEMT and MIS-FET deliver similar small positive-bias temperature instability, while the negative-bias temperature instability of the MIS-HEMT is much larger than that of MIS-FET. The MIS-FET also delivers a higher ${V}_{\text {TH}}$ stability than the MIS-HEMT under dynamic gate bias stress. It is suggested that the differences in ${V}_{\text {TH}}$ stability mainly originate from the different spatial separation between the trap states and the conducting channel, with it being larger in MIS-HEMT than in MIS-FET. [ABSTRACT FROM AUTHOR]

In this paper, we systematically investigated the leakage and breakdown mechanisms of the low-pressure chemical vapor deposition (LPCVD) silicon nitride thin film deposited on AlGaN/GaN heterostructures. The LPCVD-SiNx gate dielectric exhibits low leakage and high breakdown electric field. The dominant mechanism of the leakage current through LPCVD-SiNx gate dielectric is identified to be Poole–Frenkel emission at low electric field and Fowler–Nordheim tunneling at high electric field. Both electric-field-accelerated and temperature-accelerated time-dependent dielectric breakdown of the LPCVD-SiNx gate dielectric were also investigated. [ABSTRACT FROM PUBLISHER]

Low-loss reverse-conducting normally- OFF double-channel AlGaN/GaN power transistor with the built-in Schottky barrier diode (SBD) has been systematically studied. This device features the MOS-gate section and SBD-anode section paralleled to an interdigital layout along the gate width direction. A common access region that conducts current at both forward and reverse ON-states is employed, which is beneficial to reduce the conduction loss. With a MOS-HEMT/SBD finger width of ${4}~\mu \text{m}/2~\mu \text{m}$ and a total width ratio of 2:1, the device exhibits a threshold voltage of +0.8 V at a drain current of ${10}~\mu \text{A}$ /mm and a low forward ON-resistance of $12.1~\Omega \cdot \text {mm}$. The Schottky metal contacts 2-DEG directly, which results in a low reverse turn-on voltage of −0.6 V (at −1 mA/mm) and low reverse ON-state voltage of −1.7 V (at −50 mA/mm). A leakage suppression MOS field plate (FP) is applied to shield the Schottky contact from the strong electric field, leading to a low OFF-state leakage current of 14 nA/mm at +100-V drain bias and a high breakdown voltage (BV) of +698 V. The finger width and the number of fingers should be optimized. A narrow finger width benefits the current sharing at the access region, while the increasing number of fingers introduces more Schottky depletion regions along the gate width direction that degrade ${R}_{ \mathrm{\scriptscriptstyle ON}}$. [ABSTRACT FROM AUTHOR]