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This paper reports a normally-off high voltage hybrid Al2O 3/GaN gate-recessed MOSFET fabricated on silicon substrate. The normally off operation was implemented by digital gate recess using an oxidation and wet etching based AlGaN barrier remove technique. The Al2O 3/GaN MOSFET features a true normally off operation with a threshold voltage of 2 V extracted by the linear extrapolation of the transfer curve. The three terminal off-state breakdown voltage is 1650 V for the device with 30 μm gate-drain distance with floating Si substrate. The breakdown voltage is limited to 1000 V when the Si substrate is grounded. The on-resistance is 7.0 mΩ.cm2 for the device with 30 μm gate-drain distance and the power figure of merit is 388 MW/cm2. The small signal RF performance of the normally-off GaN MOSFET is also evaluated. © 2014 IEEE.

The gate forward leakage current in AlGaN/GaN high electron mobility transistors (HEMTs) is investigated. It is shown that the current which originated from the forward biased Schottky-gate contributed to the gate forward leakage current. Therefore, a fluorine-plasma surface treatment is presented to induce the negative ions into the AlGaN layer which results in a higher metal - semiconductor barrier. Consequently, the gate forward leakage current shrinks. Experimental results confirm that the gate forward leakage current is decreased by one order magnitude lower than that of HEMT device without plasma treatment. In addition, the DC characteristics of the HEMT device with plasma treatment have been studied. © 2013 Chinese Institute of Electronics.

In this letter, enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs) were demonstrated based on lateral scaling of the 2-D electron gas channel using nanochannel array (NCA) structure. The NCA structure consists of multiple parallel channels with nanoscale width defined by electron-beam lithography and dry etching. Because of the improved gate control from the channel sidewalls and partially relaxed piezoelectric polarization, the fabricated 2 μm-gate-length NCA-HEMT with a nanochannel width of 64 nm showed a threshold voltage of + 0.6 V and a higher extrinsic transconductance of 123 mS/mm, compared to-1.6 V and 106 mS/mm for the conventional HEMT with μ m-scale channel width. The scaling of threshold voltages, peak transconductance, and gate leakage as a function of the nanochannel width were investigated. Small-signal RF performance of NCA-HEMTs were characterized for the first time and compared with those of conventional HEMTs. © 2012 IEEE.

In this letter, we present the deployment of Schottky source/drain (SSD) in InAlN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) for off-state breakdown voltage improvement. The improved breakdown voltage relies on the suppression of electron injection into the buffer under the Schottky source contact. A V BD of 460 V is obtained in an SSD MISHEMT with an L GD = 10 μm, at a 170% improvement compared with that of the control MISHEMT featuring ohmic source/drain. Despite the SSD contacts, an SSD MISHEMT with a gate length of 1 μm exhibits a respectable drain current density of 416 mA/mm and a transconductance of 113 mS/mm. © 2011 IEEE.

AlGaN/GaN MOS-HEMTs on a silicon platform were realized using a CMOS-compatible gold-free process. Process modules commonly used in CMOS were used, including gate stack formation, etching modules, etc. R on of 3 mΩ.cm 2 was obtained. Breakdown voltage V BR of 800 V was achieved, the highest for L GD below 10 μm for AlGaN/GaN/Si MOS-HEMTs fabricated using a gold-free process. The devices could be generally useful for cost-competitive power switching circuits with supply voltage in the range of several hundred volts. © 2012 IEEE.

A boundary-temperature-controlled epitaxy, where the growth temperature of InN is controlled at its maximum, is used to obtain high-electronmobility InN layers on sapphire substrates by molecular beam epitaxy. The Hall-effect measurement shows a recorded electron mobility of 3280 cm 2 V -1 s -1 and a residual electron concentration of 1.47 × 10 17 cm -3 at room temperature. The enhanced electron mobility and reduced residual electron concentration are mainly due to the reduction of threading dislocation density. The obtained Hall mobilities are in good agreement with the theoretical modelling by the ensemble Monte Carlo simulation. © 2012 The Japan Society of Applied Physics.

In this report, we present a study on the exploitation of nanostructure-thin film interfaces. Here, the objective is to utilize such interfaces for developing nanostructures for advanced sensing devices, while using state-of-the-art microelectronic technology that enables batch production. In this context, growth of ZnO nanostructures on the GaN/AlGaN heterostructure layers was studied. A fabrication process, based on a hydrothermal growth method, was used for preparing the interfaces of nanostructured thin film. Samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and obtained results suggested near epitaxial quality of the hetero-interface. Field-effect transistors (FETs) based on ZnO nanorods/GaN heterostructures were fabricated and tested in a controlled gas environment. Thus, it was demonstrated that nanostructures could be exploited in unconventional ways by employing them in scalable and batch-producible conventional semiconductor devices. © 2011 Elsevier Ltd. All rights reserved.

In this article, integrated AlGaN/GaN cantilevers on (111) silicon substrate are fabricated and characterized. The process started with AlGaN/GaN HEMTs fabrication followed by a series of dry-etch-only MEMS process. To characterize the residual stress distribution, Micro-Raman spectroscopy is used and the residual stress in suspended GaN cantilever is found ∼ 90% lower after releasing. A type of micro-bending test is used to characterize the piezoresponse of AlGaN/GaN HEMT on the GaN cantilever. An output current modulation greater than 20% can be observed when the cantilever is vertically downward deflected ∼ 30 μm. © (2011) Trans Tech Publications.

The variations in surface potential and the Schottky barrier height ΦB in fluorine-plasma-treated AlxGa1-xN/GaN heterotructures are systematically studied by x-ray photoelectron spectroscopy (XPS), giving insights into the mechanisms underlying the strong threshold voltage shift in AlxGa1-xN/GaN HEMTs by the F plasma treatment technology. It is found that the treatment resulted in a fluorinated surface containing masses of AlF3, with the surface potential of Al0.25Ga0.75N/GaN heterostructure increased by ~0.38 eV during the first 60 seconds of the treatment. Annealing at 400 °C in N2 ambient for 10 minutes does not affect the surface potential, but results in quick reduction of AlF3, consistent with the relative poor thermal stability of AlF3 reported in literature. ΦB between Ni and F-plasma-treated Al0.25Ga0.75N surface was extrapolated from the shift in Ga 2p3/2 core-level and exhibits a small increase of 0.20 eV. The enhanced ΦB is much smaller than the positive shift in Vth observed from HEMTs fabricated with the same treatment conditions, suggesting that the primary factor responsible for the conversion from depletion-mode to enhancement-mode AlxGa1-xN/GaN by F plasma treatment is not the surface modifications, but rather the negative fixed charges carried by F ions in AlxGa1-xN/GaN heterostructures. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In this article, Gallium nitride (GaN) cantilevers integrated with AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated with a GaN-on-silicon platform, which is fully compatible with the standard HEMTs fabrication process. A type of micro-bending test was used to characterize the piezoresponse of AlGaN/GaN HEMT on the GaN cantilever. The modulation capability of the AlGaN/GaN heterostructures under different gate bias voltages for either high sensitivity or large output signals was demonstrated. A pulsed vibration measurement technique was used to evaluate the Young's modulus of the suspended GaN cantilevers, yielding a Young's modulus of ∼293 GPa.

A manipulation system utilizing the properties of two-dimensional electron gas (2DEG) at the interface of AlGaN/GaN and dielectrophoresis (DEP) was investigated in this study. At an applied frequency ranging from 100 kHz to 1 MHz and a potential of 20 vpeak to peak, the positive and negative DEP of the microspheres were reported for the first time by the Fluorine ion patterned and parylene covered 2DEG. In addition, by simply switching the applied frequency between 100 kHz and 500 kHz, the microspheres could come onto or get off from 2DEG region of AlGaN/GaN surface. Thus, a promising sensing scheme was proposed by combining the manipulation with sensing properties of 2DEG. This manipulation system based on 2DEG will bring much benefit to sensor applications. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

GaN based heterojunction devices, especially in the form of AlGaN/GaN high electron mobility transistors (HEMTs), are capable of delivering high-frequency power amplifiers and power switches with performances far superior than those offered by the mainstream silicon technology and other advanced semiconductor technologies. Rapid progress has been made in material growth and device processing technologies during the last decade. Meanwhile, there remain technical challenges to overcome. For example, unlike the silicon MOSFET technology, in which the devices' threshold voltage can be locally adjusted in the processing stage by ion implantation, the threshold voltage of conventional Cplane Ga-face AlGaN/GaN high electron mobility transistors (HEMTs) is mainly determined in the material growth stage, and exhibit large negative values due to the strong spontaneous and piezoelectric polarization effect, even without any intentional doping. A robust approach to modulating the local potential and local carrier concentration in AlGaN/GaN HEMTs was developed based on the fluorine plasma ion implantation technology. The most significant development based on this technology is the demonstration of self-aligned enhancement-mode (or normally-off) AlGaN/GaN HEMTs with low on-resistance. The stability of fluorine ions in III-nitride is of great importance to applications since it will ultimately determine the E-mode HEMTs' reliability. This paper attempts to address the stability of fluorine ions in III-nitride materials and devices based on a series of experimental and theoretical studies. © 2011 SPIE.