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With the fast-switching devices like GaN HEMT applying in power converters, the converters achieve higher switching frequency, higher efficiency and higher power density. As a result of the fast switching edge and high commutation speed, the issues like electromagnetic interference (EMI), overvoltage, gate protection become daunting tasks. The active gate control technique has been verified on the...
In this work, we have grown GaN nanowires using Plasma assisted Molecular beam epitaxy (PA-MBE) on Si (111) substrate. High resolution X-ray diffraction (HRXRD) characterization and scanning electron microscopy (SEM) studies were carried out to investigate the crystal structure, morphology and uniformity of the grown nanowires. These studies confirm wurtzite crystal structure and uniform growth. The...
We report here the hybrid Si/GaN microring resonator structure integrated with Si electrodes. Preliminary results on electro-optic tuning of the guided-mode resonance was in the range of 22 pm for the entire applied voltage range of −60 V to 80 V. Up to 9 dB change in the transmission was observed at the maximum applied voltage. The device might be useful for static wavelength-selectable notch filtering...
High quality germanium (Ge), III–V (GaAs, GaN) on insulator substrates (“X”-OI, X = Ge, GaAs or GaN) are demonstrated on 200 mm Si wafer. The Ge or III–V epitaxial films are grown directly on the Si donor wafers using a metal-organic chemical vapour deposition (MOCVD). The epilayers are then bonded and transferred to another Si (001) handle wafers to form various “X”-OI substrates. The quality of...
Similarly to the unipolar SiC Schottky diodes, AlGaN/GaN Schottky devices have been suggested to have a negligible reverse recovery current during turn-off and can therefore be switched at very high frequencies with low power losses [1-2]. This study aims to investigate this claim by comparing the reverse recovery characteristic of an AlGaN/GaN diode with that of a SiC diode and a fast recovery Si...
A large lattice-mismatch induced stress control technology with a low Al content AlGaN layer has been used to grow high quality GaN layers on Si substrates. The use of this technology allows for high mobility AlGaN/GaN heterostructures with electron mobility of 2240 cm2/Vs. It is demonstrated that the large lattice mismatch between the low Al content AlGaN layer and AlN buffer layer could effectively...
The control and assessment of doping in GaN nanostructures are crucial for the realization of GaN based nanodevices. In this study, we have investigated a series of Si-doped GaN nanowires (NWs) grown by molecular beam epitaxy (MBE) with a typical dimension of 2–3 µm in length, and 20–200 nm in radius. In particular, high resolution energy dispersive X-ray spectroscopy (EDX) has illustrated a higher...
GaN Cascode performance optimization for high efficient power applications is presented in this paper. Analytical equations of Cascode capacitance network (Ciss, Coss, Cgd) is demonstrated and the equations accuracy is verified through experimental measurement. Analysis shows that Cascode Cgd is determined by HV D-MISFETs Cds, LV Si FETs Cgd/Coss ratio, and extra zener diode capacitance. With low...
The fundamental possibility of the MBE GaN nanowires growth on silicon substrate with nanoscale buffer layer of silicon carbide has been demonstrated for the first time. Morphological and spectral properties of the resulting system have been studied and compared properties of GaN nanowires on silicon substrate.
The new technology of wide band gap semiconductors is said to outperform up-to-date silicon devices. High voltage Gallium Nitride (GaN) transistors, now emerging in the market, have even three times shorter switching times and even four times smaller energy losses compared to the best in-class Si devices. In this paper the performance of a 650 V GaN SSFET is evaluated and compared with the newest...
Wide-bandgap (WBG) semiconductors have attracted great attention as materials for the next-generation power devices since they have superior material properties compared to silicon (Si). The most advanced WBG semiconductor for power devices is silicon carbide (SiC). In 1987, the growth technology called “step-controlled epitaxy”, which enables single-phase (polytype) growth, was developed. In 1993–1994,...
Gallium Nitride (GaN) based power devices have the potential to achieve higher efficiency and higher switching frequency than those possible with Silicon (Si) power devices. In literature, GaN based converters are claimed to offer higher power density. However, a detailed comparative analysis on the power density of GaN and Si based low power dc-dc flyback converter is not reported. In this paper,...
GaN high voltage LED (HVLED) chips designed and fabricated for low-flicker converter-free LED drivers are reported. The HVLED chips show uniform electrical performance (forward voltage at 20 mA varies from 8.5 V to 8.7 V for 3-cell chips, 16.7 V to 17.4 V for 6-cell chips) and good linearity of output /input power up to 100W/cm2 input. Both features satisfy the demanding requirements of the novel...
This paper reports that the unclamped inductive switching (UIS) withstanding capability of high voltage GaN-HEMTs depends on the gate voltage at off-state and the substrate connection. The relation between the UIS withstanding capability and the electrical potential at gate and substrate is discussed by the results of the UIS test for GaN-HEMTs with p-type gate structure. Conclusively, the mechanism...
Integration of GaN high voltage transistors into Silicon CMOS could combine superior electrical parameters of GaN HEMTs and the huge logic functionality of Silicon CMOS. Several issues of a monolithic integration of GaN devices into CMOS like material mismatch and thermal budgets can be overcome by heterogeneous integration by micro Transfer Printing. Results of first printing experiments with small...
A silicon carbide (SiC) class E inverter for 6 MHz mid-range inductive power transfer (IPT) has been experimentally shown to offer improvements of 13% in efficiency compared to a previous state-of-the-art silicon (Si) equivalent, whilst delivering 100 W to the load. Using newly available ultra-low gate charge half-bridge GaN modules from Texas Instruments, a custom resonant gate drive has been designed...
Discrete gallium nitride high electron mobility transistors (HEMTs) are fabricated on oriented silicon, then undercut and assembled onto non-native silicon CMOS wafers by elastomer stamp micro-transfer-printing. The thin, less than 5 µm thick, gallium nitride transistors were then electrically interconnected using conventional thin-film metallization processes. Electrical measurements reveal that...
The rapid development of gallium nitride (GaN)-based wide bandgap power devices has been stirring power electronics industry for almost a decade. Advanced packaging solutions are eagerly needed to exploit the maximum potential of the high performance GaN semiconductors. Especially for devices in the cascode configuration, the design and fabrication of a suitable package are very challenging for high-frequency,...
With power converters demanding higher power density, transistors must be accommodated in an ever decreasing board space. Beyond gallium nitride based power transistors' ability to improve electrical efficiency, they must also be more thermally efficient. In this paper we will evaluate the thermal performance of chip-scale packaged enhancementmode GaN field effect transistors (eGaN® FETs) and compare...
In power transistor models, it is very important that device capacitances are modelled accurately so that switching losses, EMI filter requirements and gate timing requirements of the converter can be accurately determined. In this paper, a modelling technique utilizing modified sigmoid functions to describe the device capacitances is applied on a GaN HEMT and a silicon MOSFET to develop their corresponding...
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