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Heavily doped GaN nanochannel FinFET has been proposed and fabricated, for the first time, which does not have any p-n junction or heterojunction. In spite of its easy and simple epitaxial growth and fabrication process, the fabricated device with nanochannel width of 80 nm and gate length of 1 μm exhibited excellent off-state performances such as extremely low off-state leakage current of ~ 10-11 mA with BV of ~ 300 V and subthreshold slope of 68 mV/decade, very close to the theoretically limited value, which leads to high Ion/Ioff ratio of 107 ~ 109. The device also exhibited high on-state performances such as maximum drain current of 562 mA/mm and maximum transconductance of 138 mS/mm. The proposed nanochannel GaN FinFET can be very promising candidate not only for high performance, but also high power applications.

AlGaN/GaN Schttoky barrier diodes (SBDs) with and without in-situ silicon carbon nitride (SiCN) cap layer were investigated. The fabricated SBD with SiCN cap layer exhibited improved electrical characteristics, such as the forward turn on voltage of about 0.7 V, the forward current of 4.1 A at 1.5 V, and the reverse breakdown voltage of 630 V, compared to the corresponding values of 0.8 V, 3.8 A, and 580 V for the reference SBD without the SiCN cap layer. This improvement in the device performance of the SiCN-SBD is because the in-situ SiCN cap layer not only lowers the barrier height, but also effectively passivates the surface of the device with better surface morphology.

We have fabricated normally-off two different GaN MOSFETs with Al2O3 gate insulator with thickness of 38- and 54-nm and investigated the difference in device performance. From the C-V measurement, relatively higher threshold voltage and smaller threshold voltage shift were observed in the device with 54-nm-thick Al2O3 gate insulator compared to those of the device with 38-nm-thick Al2O3 gate insulator. Due to the decreased Cox with increased Al2O3 thickness, the device with 54-nm-thick Al2O3 gate insulator exhibited a little degraded DC performances compared to those of the device with 38-nm-thick Al2O3 gate insulator. Also, the device with 54-nm-thick Al2O3 exhibited better off-state characteristic with higher breakdown voltage than the device with 38-nm-thick Al2O3. However, no significant differences in the gate leakage characteristics were observed with low gate leakage current.

Group III-nitride semiconductors and their ternary solid solutions are very promising as the candidates for both short wavelength optoelectronics and power electronic devices [1]. The AlGaN/GaN heterostructure field-effect transistors (HFETs) have a great potential for future high-frequency and high-power applications because of the intrinsic advantages of materials such as wide band gap, high breakdown voltage, and high electron peak velocity [2–4]. Si substrate is considered as a promising candidate to replace expensive and small wafers such as sapphire and SiC, even though the GaN layer grown on Si substrate has a large strain and dislocation due to a large lattice mismatch and thermal expansion coefficient difference between the grown GaN layer and the Si substrate. The mismatch between thermal expansion coefficients is about 56%, which induces a large tensile stress and may cause a severe crack generation in the grown GaN films during the cooling process after growth. In this work, for the purpose of reducing the crack density in the AlGaN/GaN heterostructure grown on Si substrate, we have grown dot-like AlSi x C 1−x interlayer in inital growth state between AlN and Si substrate and demonstrated successful normally-on/off GaN HFET grown on silicon substrate.

A GaN based highly integrated Solid State Power Amplifier (SSPA) is developed for S-band radar applications. The power amplifier delivers more than 1 KW within a 400 MHz bandwidth with 55 dB gain and a typical 34% PAE. The SSPA includes a negative voltage supply, sequential bias circuit, and temperature sensor circuit. Its compact and lightweight design is suitable for many radar applications.

We report on AlGaN/GaN high electron mobility transistors (HEMTs) for high-power operation achieved by selective-area growth (SAG) technique based on plasma-assisted molecular beam epitaxy (PAMBE). Significant improvements in current density and on-state resistance were observed when SAG was employed. Maximum current of 1.75A and on-state resistance of 4.76mΩ cm2 were demonstrated for a large-periphery HEMT with total gate width of 5.2mm. Low Schottky gate leakage current was also realized by the suppression effect of SAG and the use of Si3N4/SiO2 gate insulators, leading to a high gate breakdown voltage of over 200V at a short gate-to- drain distance of 6µm.

AlGaN/GaN-based HFETs are very attractive for RF and power applications due to their superior properties, such as large critical electric field, a high two-dimensional electron gas (2DEG), and a saturation velocity compared to Si-, GaAs- and SiC-based devices. State-of-the-art performances of the AlGaN/GaN HFET already showed that f T = 160 GHz and f max = 190 GHz, and outpower = 32.2 W/mm, which were achieved mostly on normally-on device [1~2]. In some applications, for example a power switching, normally-off operation is very important to simplify the design of driving circuits and to reduce power loss during switching. However, it is very difficult to realize normally-off operation from AlGaN/GaN HFETs due to inherently large polarizaion charge at AlGaN/GaN hetero-interface. Many efforts have been given to achieve a successful normally-off operation by fabricating a schottky gate type or a MOS gate type technology [3~4].

We present a topology to provide tolerate quadrature signals in a MB-OFDM UWB frequency synthesizer. This frequency synthesizer is modified to replace a RC-CR network (RC-CR phase shifter) with a frequency division network (dual-mode divider), eliminating amplitude and phase errors of the RC-CR network. The proposed topology obtains superior suppression of image sideband of -15.5 dB when mismatches of RC passive components are assumed, based on the Monte Carlo simulation.

Due to the wide spread of Internet services, the WDM (wavelength division multiplexing) optical transmission system has been developed to meet the tremendous traffic. The WDM optical transmission system needs operation management system to manage the system efficiently and stably. The operation management system requires information of the configuration, performance, and fault state to manage the system and has the functions of OAM&P (operations, administrations, maintenance and provisioning). This paper shows the structure of the performance management functions and the object-oriented modeling method implemented to the performance management block in the 1.6T WDM OAM&P S/W system. We show how the distributed object-oriented modeling method can be applied to the performance management block and the design and implementation of the performance management block. Also, we analyzed the system software availability implemented by the object-oriented modeling method from the viewpoint of reusability and maintainability.