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The current transport properties of Pt Schottky contacts on free standing bulk GaN measured at 300–425 K are reported in this article. The analysis on the experimental forward current characteristics based on Tung’s model, considering an effective area due to the presence of local inhomogeneous barrier, produced the Richardson constant similar to the theoretical value. The reverse leakage current characteristics at high temperatures were described well with the thermionic field emission model. Unexpectedly high leakage current at low temperatures was analytically described by using the dislocation-related tunneling current at low bias voltages. In addition, the trap-assisted tunneling was observed to contribute to the leakage current at high voltages. The result in this work is beneficial in diagnosing the properties of vertical GaN Schottky diodes, especially the role of dislocations in the leakage current. [ABSTRACT FROM AUTHOR]

This paper reviews the near-equilibrium ammonothermal (NEAT) growth of bulk gallium nitride (GaN) crystals and reports the evaluation of 2″ GaN substrates and 100 mmbulk GaN crystal grown in our pilot production reactor. Recent progress in oxygen reduction enabled growing NEAT GaN substrates with lower residual oxygen, coloration, and optical absorption. The oxygen concentration was approximately 2 × 1018 cm−2, and the optical absorption coefficient was 1.3 cm−1 at 450 nm. Maps of full-width half maximum (FWHM) of X-ray diffraction rocking curveswere generated for grown crystals and finished wafers. The X-ray rocking curve maps confirmed high-quality and uniform microstructure across the entire surface of the bulk crystals and substrates. The average FWHM of the 50 best bulk crystals from the recent batch was 28 ± 4 arcsec for the 002 diffraction and 34 ± 5 arcsec for the 201 diffraction, with an average radius of curvature of 20 m. X-ray topography measured on both sides of the bulk crystals implied that the density of dislocations wasreduced by one order of magnitude during the NEAT growth. A typical NEAT GaN substrate shows dislocation density of about 2 × 105 cm−2. [ABSTRACT FROM AUTHOR]

Wide band gap III-nitride materials have gained considerable attention as promising semiconductor materials for light-emitting photonic diodes and high-frequency/power devices. However, the material quality of GaN grown on foreign substrates has hindered the achievement of theoretically superior properties of GaN in commercialized real devices. GaN epilayers grown on GaN substrates (GaN-on-GaN) offer a lower dislocation density and thus a higher epitaxial quality of GaN. However, the critical issues of metal contacts to bulk GaN, such as barrier height, leakage currents, and interfacial states, can limit the performance of bulk GaN-based devices. In this review, Schottky metal contacts to bulk GaN are described, and their electrical characterization is discussed in terms of the barrier formation and current transport mechanisms, namely: (1) Schottky barrier inhomogeneity, (2) Schottky barrier modulation by an ultrathin interlayer, (3) leakage current transport, (4) dislocation-related current transport, and (5) deep level defects. However, the dislocation density in GaN-on-GaN remains high. Therefore, further research for clarifying the correlation between current conduction and point/extended defects is necessary to enhance the performance and reliability of bulk GaN-based devices. [ABSTRACT FROM AUTHOR]

Summary: Gallium nitride (GaN) is a promising semiconductor material for the application of the high power electronic, optoelectronic, laser diodes, etc. The previous works have been focused on the electronic and optical properties of the monolayer GaN. However, the structural, electronic and optical properties of the bulk GaN are unclear. In particular, the role of N‐vacancy on the electronic and optical properties of the bulk GaN is unknown. In this work, we apply first‐principles calculations to study the influence of N‐vacancy on the structural, electronic and optical properties of the bulk GaN. Three bulk GaN: hexagonal (P63/mc), cubic (F‐43m) and cubic (Fm‐3m) are considered. The result shows that the N‐vacancy is thermodynamic stability in bulk GaN. The thermodynamic stability of the GaN with the N‐vacancy is demonstrated by the change of Ga–N bond. Three GaN show the semiconductor feature because of the role of N‐2p state. The calculated band gap of GaN with the P63mc, F‐43m and Fm‐3m is 1.651, 1.489 and 0.450 eV. However, the N‐vacancy enhances the electronic jump of GaN because the N‐vacancy induces the move of the position of Fermi level to the region of the conduction band. The metallic behavior of GaN with the N‐vacancy is demonstrated by the dielectric function diagram. In particular, the N‐vacancy gives rise to the visible light region optical adsorption compared to the corresponding bulk GaN. [ABSTRACT FROM AUTHOR]

This paper reviews the near-equilibrium ammonothermal (NEAT) growth of bulk gallium nitride (GaN) crystals and reports the evaluation of 2″ GaN substrates and 100 mmbulk GaN crystal grown in our pilot production reactor. Recent progress in oxygen reduction enabled growing NEAT GaN substrates with lower residual oxygen, coloration, and optical absorption. The oxygen concentration was approximately 2 × 1018 cm−2, and the optical absorption coefficient was 1.3 cm−1 at 450 nm. Maps of full-width half maximum (FWHM) of X-ray diffraction rocking curveswere generated for grown crystals and finished wafers. The X-ray rocking curve maps confirmed high-quality and uniform microstructure across the entire surface of the bulk crystals and substrates. The average FWHM of the 50 best bulk crystals from the recent batch was 28 ± 4 arcsec for the 002 diffraction and 34 ± 5 arcsec for the 201 diffraction, with an average radius of curvature of 20 m. X-ray topography measured on both sides of the bulk crystals implied that the density of dislocations wasreduced by one order of magnitude during the NEAT growth. A typical NEAT GaN substrate shows dislocation density of about 2 × 105 cm−2.

Abstract In this study unintentionally doped GaN grown by hydride vapor phase epitaxy that exhibits a sharply delimited region of green color was investigated. Optical analysis was performed by absorption and photoluminescence spectroscopy. An absorption band between 1.5 and 2.0 eV was found to be responsible for the green color and was related to a sharp emission at 1.193 eV by luminescence and excitation spectroscopy. The appearance of both optical signatures in the region of green color was related to an increase of Cr contamination detected by secondary ion mass spectrometry. We propose that the origin of green color as well as the emission line at 1.193 eV is attributed to internal transitions of Cr 4 +. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly uniform MoS 2 heterojunctions with low-dislocation density bulk GaN have been fabricated by a two-steps CVD growth. • Atomic resolution electron microscopy of the MoS 2 /GaN interface revealed a nearly ideal van der Waals junction • Raman mapping showed very low strain and a significant p-type doping of the MoS 2 film. • Local I-V analyses on the MoS 2 /n-GaN heterojunction showed a rectifying behavior, with an onset voltage V on =1.7 V. The integration of two-dimensional MoS 2 with GaN recently attracted significant interest for future electronic/optoelectronic applications. However, the reported studies have been mainly carried out using heteroepitaxial GaN templates on sapphire substrates, whereas the growth of MoS 2 on low-dislocation-density bulk GaN can be strategic for the realization of "truly" vertical devices. In this paper, we report the growth of ultrathin MoS 2 films, mostly composed by single-layers (1L), onto homoepitaxial n−-GaN on n+ bulk substrates by sulfurization of a pre-deposited MoO x film. Highly uniform and conformal coverage of the GaN surface was demonstrated by atomic force microscopy, while very low tensile strain (∼0.05%) and a significant p+-type doping (∼4.5 × 1012 cm−2) of 1L-MoS 2 was evaluated by Raman mapping. Atomic resolution structural and compositional analyses by aberration-corrected electron microscopy revealed a nearly-ideal van der Waals interface between MoS 2 and the Ga-terminated GaN crystal, where only the topmost Ga atoms are affected by oxidation. Furthermore, the relevant lattice parameters of the MoS 2 /GaN heterojunction, such as the van der Waals gap, were measured with high precision. Finally, the vertical current injection across this 2D/3D heterojunction has been investigated by nanoscale current-voltage analyses performed by conductive atomic force microscopy, showing a rectifying behavior with an average turn-on voltage V on = 1.7 V under forward bias, consistent with the expected band alignment at the interface between p+ doped 1L-MoS 2 and n-GaN. [ABSTRACT FROM AUTHOR]

In this paper, the advantages of GaN high electron mobility transistors (HEMTs) grown on native GaN over GaN/Si or GaN/sapphire substrates are investigated and correlated with epitaxial material quality. Transmission electron microscopy plan-view and cross-sectional analyses of GaN/GaN reveal dislocation densities below ${1} \times {10}^{{6}}$ cm−2, which is at least three orders of magnitude lower than that of GaN/Si or GaN/sapphire. In the case of GaN/Si, the dislocations not only originate from the substrate/nucleation layer interface, but also the strain relief and isolation buffer stacks are main contributors to the dislocation density. GaN/GaN HEMTs show superior electrical and thermal performance and feature three orders of magnitude lower OFF-state leakage. The current collapse (also referred to as current dispersion or $R_{ \mathrm{\scriptscriptstyle ON}}$ -increase) after stress bias is less than 15% compared with 50% in the case of GaN/Si. A 2% drop of the ON-state current due to self-heating in dc operation when compared with 13% and 16% for GaN/Si and GaN/sapphire, respectively. The GaN/Si thermal performance becomes comparable to that of GaN/GaN only after substrate removal. Therefore, GaN/GaN provides high ON-state current, low OFF-state leakage current, minimal current collapse, and enhanced thermal power dissipation capability at the same time, which can directly be correlated with the absence of high dislocation density. [ABSTRACT FROM AUTHOR]

This letter reports on the dynamic $R_{\text{ON}}$ performance of large-area GaN vertical trench MOSFETs (OG-FETs) fabricated on bulk GaN substrates. OG-FETs demonstrated excellent DC performance with a breakdown voltage of 900 V and a $R_{\text{ON}}$ of 4.1 $\Omega$ (8.2 $\text{m}\Omega \cdot \text {cm}^{2}$ ). However, damage to the trench sidewalls caused by RIE dry etching led to poor dynamic $R_{\text{ON}}$ performance. An improved dynamic $R_{\text{ON}}$ performance was achieved by following the RIE dry etch with a TMAH wet etch. With this process combination, the dynamic $R_{\text{ON}}$ was reduced by more than 10 times compared with the dynamic $R_{\text{ON}}$ in devices fabricated by dry etch only. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) is a promising candidate for high‐power and high‐frequency devices. To date, the lack of large area bulk GaN materials of reasonable cost and quality has limited the technology almost completely to lateral devices. However, vertical structures are attractive to obtain a higher current density and a reduced device size. In this work, the electrical behavior of a Ni/Au Schottky barrier on bulk GaN material is studied, using vertical Schottky diodes. The forward current–voltage characteristics of the diodes reveal a temperature dependence of both the ideality factor (n) and of the Schottky barrier height (ΦB). The ideal value of the barrier of 1.72 eV extrapolated at n = 1 is in agreement with the results obtained by capacitance–voltage measurements. A nanoscale electrical analysis performed by conductive atomic force microscopy (C‐AFM) allow to visualize the barrier height inhomogeneity and to correlate the current distribution to the surface morphology of the material. The barrier inhomogeneity explains the temperature behavior of ideality factor and barrier height determined by the macroscopic diodes. Preliminary structural analyses carried out by transmission electron microscopy (TEM) of the metal semiconductor interface revealed a typically flat Au/Ni bilayer structure, the Ni layer being epitaxial to GaN, with some mosaicity. [ABSTRACT FROM AUTHOR]

• SAW filter with an insertion loss (IL) of 4.415 dB has been demonstrated on c -plane bulk GaN, which is the minimum IL of GaN-based SAW filters. • The impact of number of interdigital transducers, and acoustic propagation direction on the performance of filters has been studied. • The numerical distribution of elastic stiffness and piezoelectric constants of bulk GaN has been calculated in Euler angle space. Surface acoustic wave (SAW) filter with a low insertion loss (IL) of 4.415 dB has been demonstrated on Carbon-doped semi-insulating c -plane bulk GaN without external lumped element matching. The center frequency, 3 dB bandwidth, out-of-band attenuation, return loss of the filter are 477.05 MHz, 0.308 MHz, 32.5 dB, and −9.72 dB, respectively. The electromechanical coupling coefficient (K t 2), and temperature coefficient of frequency (TCF) of the filter are 0.21 % and −26.0 ppm/°C, respectively. The impact of the number of interdigital transducers (N IDT) and acoustic propagation direction on filter performance has been studied. The IL of filters reduces from 16.07 dB to 4.415 dB with the increase of N IDT from 50 to 150 due to the enhanced acoustic superposition. The numerical distribution of elastic stiffness ([ c ij ]), and piezoelectric constants ([ e ik ]) of GaN has been calculated in Euler angle space, indicating that they are isotropic on c -plane. The small performance difference of filters along the m - and a -direction on c -plane bulk GaN can be attributed to the small offset angle of 0.5° of the bulk GaN wafer or IDT quality variation. [ABSTRACT FROM AUTHOR]

In this article we investigated unintentionally doped (UID) GaN grown by hydride vapor phase epitaxy (HVPE) with respect to point defects and impurity concentration. The samples were orange tinted to different extent. Optical analysis was performed by micro-photoluminescence and absorption spectroscopy. Absorption measurements revealed an absorption peak at 1.5 eV related to an internal transition in Mn 3 + impurities and a second band with low energy onset at 1.9 eV, both increasing with the extent of orange color. Electron paramagnetic resonance investigations showed the presence of Mn 2 + and Fe 3 + in the colored crystals. The overall impurity concentration was verified by secondary ion mass spectrometry. Orange tint is associated with an increase of transition metal contamination, especially Mn. Based on these observations we suggest that the orange coloring in the investigated UID HVPE GaN samples is caused by the presence of Mn impurities. [ABSTRACT FROM AUTHOR]

Native bulk gallium nitride (GaN) has emerged as an alternative for sapphire and silicon as a substrate material for III-N devices. While quasi-bulk GaN substrates are currently commercially available, single crystal GaN substrates are considered essential for future high performance light emitters and power devices. The ammonothermal method is currently considered one of the most feasible methods to grow large truly bulk crystals of GaN at low cost and high structural quality. High crystalline quality GaN substrates sliced from ammonothermally grown crystals have been demonstrated and utilized in homoepitaxy for III-N devices. However, despite the high crystalline quality the properties of as-grown ammonothermal GaN crystals and substrates are affected by the presence of impurities and other defects that hinder their use for device applications. Here, the main developments of ammonothermal growth of GaN and the effects of impurities, native point defects, and dislocations on the material properties are summarized. Additionally, measurement techniques that enable the evaluation of point defect concentration and low dislocation density distribution over a large area on bulk GaN substrates are reviewed. [ABSTRACT FROM AUTHOR]

In this paper, the Ni Schottky barrier on GaN epilayer grown on free standing substrates has been characterized. First, transmission electrical microscopy (TEM) images and nanoscale electrical analysis by conductive atomic force microscopy (C-AFM) of the bare material allowed visualizing structural defects in the crystal, as well as local inhomogeneities of the current conduction. The forward current-voltage (I-V) characteristics of Ni/GaN vertical Schottky diodes fabricated on the epilayer gave average values of the Schottky barrier height of 0.79 eV and ideality factor of 1.14. A statistical analysis over a set of diodes, combined with temperature dependence measurements, confirmed the formation of an inhomogeneous Schottky barrier in this material. From a plot of Φ B versus n, an ideal homogeneous barrier close to 0.9 eV was estimated, similar to that extrapolated by capacitance-voltage (C V) analysis. Local I-V curves, acquired by means of C-AFM, displayed the inhomogeneous distribution of the onset of current conduction, which in turn resembles the one observed in the macroscopic Schottky diodes. Finally, the reverse characteristic of the diodes fabricated in the defects-free region have been acquired at different temperature and its behaviour has been described by the thermionic field emission (TFE) model. [Display omitted] • Structural defects have been observed by TEM images and Conductive - AFM analysis • Inhomogeneous barrier revealed by macroscopic and nanoscale electrical analysis • Origin of the Inhomogeneous barrier has been ascribed to electrical active defects [ABSTRACT FROM AUTHOR]

In this paper, crack-free 2-inch bulk GaN wafer with the thickness up to 3 mm was obtained by HVPE homoepitaxy. A new method of acid wet etching was used to pre-treat GaN substrate before re-growth. The formation of the mesh-like subsurface crack and interface layer were found to be suppressed between the re-growth layer and as-grown GaN substrate. EDS and time varied contact angle measurement proved that chemical etching would decrease the oxygen related surface adsorption and increase atoms diffusion length during HVPE homoepitaxial growth. Moreover, Morphology, Low temperature photoluminescence measurements indicated a reduction in stress of wet etching treated as-grown GaN substrate due to etching effect on its N face. High quality bulk GaN with the dislocation density of 1×10 6 cm −2 was achieved by using wet etching and HVPE multiple re-growth. It would offer a simple method to obtain bulk GaN with thicker layer and high quality. [ABSTRACT FROM AUTHOR]

There is a great interest in wide-bandgap semiconductor devices and most recently in monolithic GaN structures for power electronics applications. In this paper, vertical p-n diodes fabricated on pseudobulk low defect density ( 10^4 – 10^6 cm ^-2 ) GaN substrates are discussed. Homoepitaxial low-pressure metal organic chemical vapor deposition growth of GaN on its native substrate and being able to control and balance the n-type Si doping with background C impurity has allowed the realization of vertical device architectures with drift layer thicknesses of 6 to 40 \mu m and net carrier electron concentrations of 4\times 10^{15} to 2.5\times 10^{16} cm ^-3 . This parameter range is suitable for applications requiring breakdown voltages (BVs) of 600 V–4 kV with a proper edge termination strategy. Measured devices demonstrate near power device figure of merit, that is, differential specific on-resistance ( R{{\textrm {sp}}} ) of 2 m \Omega cm ^{2} for a BV of 2.6 kV and 2.95 m \Omega cm ^2 for a 3.7-kV device, respectively. The improvement in the substrate quality over the last few years has resulted in the fabrication of diodes with areas as large as 16 mm ^2 , with BVs exceeding 700 V and pulsed (100 $\mu $ s) currents of 400 A. The structures fabricated are utilized to study in detail the temperature dependency of $I$ – $V$ characteristics, impact ionization and avalanche characteristics, and extract (estimate) modeling parameters such as electron mobility in the GaN $c$ -direction (vertical) and hole minority carrier lifetimes. Some insight into device reliability is also provided. [ABSTRACT FROM AUTHOR]

In this study, the optical, structural, electrical and thermoelectric properties of undoped and Si-doped bulk GaN samples are investigated. The room temperature PL near band emission peaks of undoped and Si-doped bulk GaN samples are 3.414 eV and 3.402 eV. The undoped and Si-doped bulk GaN samples' PL spectra have different defect emission bands which are green band and red band with the maximum at 2.4 eV and 2.0 eV, respectively. At low temperature, the PL spectrum of undoped bulk GaN has well-defined excitonic emission lines, A0X, D0X, FXA (n = 1, 2), while the PL spectrum of Si-doped bulk GaN has just broad emission peaks at the similar energy level. The low temperature PL spectra of both undoped and Si-doped samples clearly show the first, second and third longitudinal-optical phonon (1 LO, 2 LO and 3 LO) replicas. There are no donor-acceptor pairs and electron-acceptors' emission in the PL spectra of the samples. The temperature dependence PL spectra of undoped GaN samples shows that the intensity ratio of the FXA to D0X decreases with the increase of the temperature. The full width at half maximum (FWHM) of D0X emission is about 4.7 meV. The carrier density of the undoped and Si-doped bulk GaN are 4.58 × 1015 and 2.41 × 1018 cm--3, and the mobility of the undoped and Si-doped bulk GaN are 1050 and 286 cm2V-1s-1. The FWHM of (0002) X-ray diffraction rocking curve are 54 arcsec and 95 arcsec for the undoped and Si-doped bulk GaN samples. The power factors of the undoped GaN sample and the Si-doped GaN sample are 0.315 × 10-4W/mK2 and 0.35495 × 10-4 W/mK2, respectively. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Cathodoluminescence (CL) spectroscopy and mapping techniques were used to study defect and impurity distributions in free-standing bulk GaN substrates prepared by hydride vapor-phase epitaxy. It was found that, in the bulk GaN substrates investigated, dislocation clusters appearing as dark cores in the CL map were surrounded by bright disk-like regions with higher luminescence efficiency than that of the outside areas. This large-area luminescence nonuniformity disappeared in homoepitaxial GaN grown on top of the GaN substrate. Schottky barrier diodes fabricated on the homo-epilayer exhibited low average reverse leakage current, while dislocation clusters duplicated from the original bulk GaN substrate still limited device yield. [ABSTRACT FROM AUTHOR]

We perform a transmission electron microscopy (TEM) characterization of blue light-emitting diode epiwafers grown homoepitaxially on a c-plane GaN substrate and compare with such grown on sapphire. We find a threading dislocation (TD) density as low as 2 x 108 cm-2 in homoepitaxial growth, which is 1/30 of that in sapphire-based material. A unique type of inverted pyramid defect with diameter ~650 nm was observed. It originates from the homo-interface in edge-type TDs. TDs were also found to be generated within the quantum wells without a precursor TD defect. Otherwise, high-resolution TEM suggests extremely homogeneous quantum wells and barriers in terms of composition and well width. Besides plan-view TEM, wet chemical etching on n-type GaN was carried out in hot phosphoric acid to evaluate the TD density more quickly. The two methods prove to be equivalent with respect of determined TD densities. [ABSTRACT FROM AUTHOR]

We present a junction temperature analysis of GaInN/GaN quantum well (QW) light-emitting diodes (LEDs) grown on sapphire and bulk GaN substrate by micro-Raman spectroscopy. The temperature was measured up to a drive current of 250 mA (357 A/cm²). We find better cooling efficiency in dies grown on GaN substrates with a thermal resistance of 75 K/W. For dies on sapphire substrates we find values as high as 425 K/W. Poor thermal performance in the latter is attributed to the low thermal conductivity of the sapphire. Three-dimensional finite-element simulations show good agreement with the experimental results, validating our thermal model for the design of better cooled structures. [ABSTRACT FROM AUTHOR]

Inductive avalanche test results presented in this letter demonstrate that GaN p-n diodes can sustain single-pulse and repetitive inductive avalanche currents. The 0.36-mm2 vertical GaN p-n diodes can sustain single-pulse avalanche currents as high as 10 A. The safe zone of the single-pulse avalanche current is limited by peak pulse power and energy deposited in the device. The temperature-dependent behavior of the breakdown voltage and the reverse-voltage at onset of avalanche has a positive temperature coefficient. Repetitive avalanche ruggedness testing was performed by applying 10^\mathrm 5 pulses at 5-kHz frequency with increasing repetitive stress current. Based on a population of 63 devices, the incremental failure rate under repetitive avalanche current increases with increasing avalanche current. The devices that survive the step stress test sustain no parametric drift under repetitive avalanche. [ABSTRACT FROM AUTHOR]

Reactive ion etching of {0001} oriented plate-like GaN single crystals has been investigated using SiCl4:Ar:SF6 chemistry. The reactive ion etching process is highly chemical. Large anisotropy of the etching rate and of the morphology has been established on (000 $$\bar 1$$ ) N-polar and (0001) Ga-polar sides of the GaN crystals, with remarkably higher rate on the N-polar side. Atomic force microscopy measurements have shown smooth surface and good polishing effect obtained on Ga-polar side, while N-polar surface exhibits an increased roughness of a factor of 10 after RIE. [ABSTRACT FROM AUTHOR]

This paper describes TEM characterization of bulk GaN crystals grown at 1500-1800Kin the form of plates from a solution of atomic nitrogen in liquid gallium under high nitrogen pressure (up to 20 kbars). The x-ray rocking curves for these crystals were in the range of 20-30 arc-sec. The plate thickness along the c axis was about 100 times smaller than the nonpolar growth directions. A substantial difference in material quality was observed on the opposite sides of the plates normal to the c direction. On one side the surface was atomically flat, while on the other side the surface was rough, with pyramidal features up to 100 nm high. The polarity of the crystals was determined using convergent-beam electron diffraction. The results showed that, regarding the long bond between Ga and N along the c-axis, Ga atoms were found to be closer to the flat side of the crystal, while N atoms were found to be closer to the rough side. Near the rough side, within 1/10 to 1/4 of the plate thickness, there was a high density of planar defects (stacking faults and dislocation loops decorated by Ga/void precipitates). A model explaining the defect formation is proposed. [ABSTRACT FROM AUTHOR]

The reliability of AlGaN/GaN HEMTs processed on bulk GaN substrates was studied using electrical and optical methods, showing a decreasing degradation with increasing base-plate temperature (Tb). Generation of traps spatially located in both intrinsic and extrinsic HEMT regions was found to be most pronounced for off-state bias stress performed at room Tb, while increasing Tb up to 150 ^\circ\C decreased trap generation underneath the gate perimeter. This was attributed to degradation driven by hot electrons as it should dominate over defect-related degradation mechanisms in GaN-on-GaN devices. [ABSTRACT FROM AUTHOR]