Journal of Applied physics,Vol.33 : 1962年に発表されたレオロジー関連の論文

Nuclear Instruments and Methods in Physics Research. Section B; Microstructural Characterization of Semi-Interpenetrating Polymer Networks by Positron Lifetime Spectroscopy

(IEEE Transactions on Electron Devices,36(12):2816-2820)Field-Drifting Resonant Tunneling Through a-Si:H/a-Sil-xCx:H Quantum Wells at Different Locations of the i-Layer of a p-i-n Structure

An RF switch circuit and method for switching RF signals that may be fabricated using common integrated circuit materials such as silicon, particularly using insulating substrate technologies. The RF switch includes switching and shunting transistor groupings to alternatively couple RF input signals to a common RF node, each controlled by a switching control voltage (SW) or its inverse (SW_), which are approximately symmetrical about ground. The transistor groupings each comprise one or more insulating gate FET transistors connected together in a “stacked” series channel configuration, which increases the breakdown voltage across the series connected transistors and improves RF switch compression. A fully integrated RF switch is described including control logic and a negative voltage generator with the RF switch elements. In one embodiment, the fully integrated RF switch includes an oscillator, a charge pump, CMOS logic circuitry, level-shifting and voltage divider circuits, and an RF buffer circuit.

Switch Circuit and Method of Switching Radio Frequency Signals

Ohmic contacts to Gallium Nitride materials

A mechanism of the formation of the bulges on the surface of Ti/Al/Ni/Au Ohmic contact in AlGaN/GaN high electron mobility transistors is proposed. According to the analysis of TEM images and corresponding electron dispersive x-ray spectra, the bulges were found to consist of Ni–Al alloy in the body and Au–Al alloy surrounding. We deduce that the bulges were formed due to Ni–Al alloy aggregation in some local areas during the rapid thermal annealing process, which accounts for the rough surface morphology.

Analysis of surface roughness in Ti/Al/Ni/Au Ohmic contact to AlGaN/GaN high electron mobility transistors

A self-terminating gate recess etching technique is first proposed to fabricate normally off AlGaN/GaN MOSFET. The gate recess process includes a thermal oxidation of the AlGaN barrier layer for 40 min at 615°C followed by 45-min etching in potassium hydroxide solution at 70°C, which is found to be self-terminated at the AlGaN/GaN interface with negligible effect on the underlying GaN layer, manifesting itself easy to control, highly repeatable, and promising for industrialization. The fabricated device based on this technique with atomic layer deposition Al2O3 as gate insulator exhibits a threshold voltage as high as 3.2 V with a maximum drain current over 200 mA/mm and a 60% increased breakdown voltage than that of the conventional high electron mobility transistors.

Fabrication of Normally Off AlGaN/GaN MOSFET Using a Self-Terminating Gate Recess Etching Technique

Based on our proposed self-terminating gate recess etching technique, normally-off recess-gated AlGaN/GaN MOSFET has been demonstrated with a novel method using GaN cap layer (CL) as recess mask, which, as a result, simplifies the device fabrication process and lowers the fabrication cost. The GaN CL is capable of acting as an effective recess mask for the gate recess process, which includes a thermal oxidation for 45 min at 650 degrees C followed by 4-min etching in potassium hydroxide (KOH) at 70 degrees C. After gate recess process, no obvious change is observed in terms of the surface morphology of the GaN CL, the contact resistance of the Ohmic contact formed directly on the GaN CL as well as the sheet resistance of the two-dimensional electron gas (2-DEG) channel layer under the GaN CL. The fabricated device exhibits a threshold voltage (V-th) as high as 5 V, a maximum drain current (I-dmax) of similar to 200 mA/mm, a high ON/OFF current ratio of similar to 10(10) together with a low forward gate leakage current of similar to 10(-5) mA/mm. Meanwhile, the OFF-state breakdown voltage (V-br) of the device with gate-drain distance of 6 mu m is 450 V.

Demonstration of Normally-Off Recess-Gated AlGaN/GaN MOSFET Using GaN Cap Layer as Recess Mask

In this letter, a plasma-free etch stop structure is developed for GaN HEMT toward enhancement-mode operation. The self-terminated precision gate recess is realized by inserting a thin AlN/GaN bilayer in the AlGaN barrier layer. The gate recess is stopped automatically at the GaN insertion layer after high-temperature oxidation and wet etch, leaving a thin AlGaN barrier to maintain a quantum well channel that is normally pinched off. With addition of an Al2O3 gate dielectric, quasi normally OFF GaN MOSHEMTs have been fabricated with high threshold uniformity and low ON-resistance comparable with the normally ON devices on the same wafer. A high channel mobility of 1400 cm $^{2}/\textrm {V}\cdot \textrm {s}$ was obtained due to the preservation of the high electron mobility in the quantum-well channel under the gate.

A GaN HEMT Structure Allowing Self-Terminated, Plasma-Free Etching for High-Uniformity, High-Mobility Enhancement-Mode Devices

High temperature characteristics of GaN-based inverter is presented from room temperature (RT) to 300 °C, which is integrated with enhancement-mode MOSFET and depletion-mode HEMT. At 300 °C, the fabricated inverter operates properly at a supply voltage (VDD) of 7 V with 6.5 V for logic voltage swing, 3.3 V for threshold voltage (VTH), 2.4 V for logic-low noise margin (NML), and 3.4 V for logic-high noise margin (NMH). Meanwhile, the inverter exhibits small variations from RT to 300 °C in terms of logic voltage swing, VTH, NML, and NMH with the maximum relative variations of 2.2%, 5.7%, 12.9%, and 4.9% in such temperature range, respectively.

Min Yu

Papers

Analysis of surface roughness in Ti/Al/Ni/Au Ohmic contact to AlGaN/GaN high electron mobility transistors

Fabrication of Normally Off AlGaN/GaN MOSFET Using a Self-Terminating Gate Recess Etching Technique

Demonstration of Normally-Off Recess-Gated AlGaN/GaN MOSFET Using GaN Cap Layer as Recess Mask

A GaN HEMT Structure Allowing Self-Terminated, Plasma-Free Etching for High-Uniformity, High-Mobility Enhancement-Mode Devices

High Temperature Characteristics of GaN-Based Inverter Integrated With Enhancement-Mode (E-Mode) MOSFET and Depletion-Mode (D-Mode) HEMT