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This article attempts to disclose a high-efficiency laser driver that controls laser sources for high-frequency light detection and ranging (LiDAR) applications. The specific LiDAR requisites encompass a 20-MHz laser repetition rate, a 10-ns pulse duration, and an instantaneous power of 50 W. The power efficiency of a LiDAR used in autonomous vehicles is critical, which shall yield a total input power within 15 W. To enhance power efficiency, a half-bridge pulse laser drive is proposed, featuring a depletion mode gallium nitride (D-mode GaN) transistor on the high-side and an enhancement mode (E-mode) GaN transistor on the low-side. A high-side gate drive is also introduced and analyzed for the D-mode GaN transistor, which can greatly minimize oscillation during laser-pulse capacitor charging due to no body diode effect. Key efficiency factors include the equivalent series resistance of multilayer ceramic capacitor, high-side transistor switching loss, and transistor resistive loss. A peak efficiency of 75% is found at the compromise of all losses, which is verified in both theoretical and experimental methods. The pulse laser drive operation is proven to be stable in the experiments over a wide range of laser repetition rates from 10 kHz to 20 MHz.

In this study, quaternary InAlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) aimed for power applications were exposed to 800 krad of Co $^{60}~\gamma $ -ray, and their response to total dose effects was recorded. For the irradiation process, devices with five gate-connected field plate schemes of field plate length (without field plate, $2~\mu $ m, 4, $\mu $ m, $6~\mu $ m, $8~\mu $ m) were tested under either a grounded state or a stressed state. It was discovered that the implementation of the field plate could successfully suppress the virtual gate phenomenon exacerbated by total dose effects. Post-irradiation analysis of the reverse characteristics also revealed that for devices irradiated under a stressed state, field plates could increase the device robustness against total dose effects impacting the electrical breakdown.

In this study, we empirically explore the performance degradation of quaternary InAlGaN/AlN/GaN Metal-Insulator-Semiconductor High Electron Mobility Transistors (MIS-HEMTs) with a Gate Field Plate (GFP) structure under a Positive Bias Temperature Instability (PBTI) and Negative Bias Temperature Instability (NBTI) stresses. Both stress conditions (PBTI with V ${_{\text {GS}}} = 10$ V and NBTI with V ${_{\text {GS}}} {=} -30$ V) are applied. The experimental findings reveal a positive shift in threshold voltage (VTH), indicating the presence of a net negative charge beneath the gate area. However, we find distinct degradation dynamics for both stress experiments. During PBTI, the ${\mathrm { V}}_{\mathrm { TH}}$ shift remains temperature independent, suggesting the generation of defects leading to electron trapping in the insulator. In NBTI, critical defects are identified, resulting in a permanent ${\mathrm { V}}_{\mathrm { TH}}$ shift with temperature dependence. Furthermore, the extracted activation energy (Ea) from Arrhenius plots in PBTI is determined to be 0.14 eV and 0.11 eV, highlighting the crucial role of shallow C-related traps governed by the Shockley-Read Hall (SRH) recombination process. In contrast, for NBTI, ${\mathrm { E}}_{\mathrm { a}} = 0.12$ eV, indicating the involvement of surface traps and thermal-assisted de-trapping kinetics, leading to the generation of permanent defects. These results underscore the distinct dynamics of performance degradation phenomena in PBTI and NBTI involves different trap energies at different locations within the device structure.

This experimental study investigates the traps dynamics and threshold voltage (VTH) shift mechanism under negative bias temperature stress for the GaN-on-Si Power MIS HEMTs on field plate design structure. Based on the experimental analysis, two distinct activation energies (Ea) have been identified under the specific reverse bias conditions of VGS= -30 V and VDS=0 V in a wide temperature range. Reverse bias stress experiments (up to 10 ks) show a positive VTH shift of ~1.6 V at room temperature due to the inversion of the charges at the interface between the insulator and AlGaN layer, resulting in net negative charge near the gate region. Subsequently, there is a decrease in VTH shift till $125~^{\circ }$ C because of the de-trapping of the inversion charges. This phenomenon shows a strong correlation with a thermally activated activation energy of (E ${_{\text {a}}}~\approx ~0.23$ eV). Further, the shift in ${\mathrm { V}}_{\mathrm { TH}}$ turns negative when the temperature is raised to $175~^{\circ }$ C, indicating the accumulation of electrons in the channel layer with activation energy (E ${_{\text {a}}}~\approx ~0.78$ eV) attributed to the activation of nitrogen interstitials from the GaN buffer layer. Additionally, the recovery (up to 10 ks) behavior demonstrates the exponential-linear settlement of the traps to recover the ${\mathrm { V}}_{\mathrm { TH}}$ shift. Moreover, nitrogen interstitials take more time to suppress the threshold voltage instabilities. These findings explain the ${\mathrm { V}}_{\mathrm { TH}}$ shift mechanisms in GaN-on-Si Power MIS HEMTs under NBTI.