Guanxi Piao

Gate-Length Dependence of DC Characteristics in Submicron-Gate AlGaN/GaN High Electron Mobility Transistors

We investigated the gate-length dependence of room-temperature DC operation in submicron-gate AlGaN/GaN high-electron-mobility transistors (HEMTs). The threshold voltage was reduced by the short-channel effect, which is only dependent on the aspect ratio of the gate length to the barrier-layer thickness. On the other hand, the transconductance was restricted by the source resistance, and was dependent on not only the gate length LG but also the source?gate length LSG. The transconductance was increased by reducing LSG rather than LG in the submicron-gate HEMTs.

GaN Crystal Growth on Sapphire Substrate Using Islandlike GaN Buffer Formed by Repetition of Thin-Layer Low-Temperature Deposition and Annealing in rf-Plasma Molecular Beam Epitaxy

We employed a new buffer growth method of superposing the thin low-temperature (LT)-grown GaN layers using an rf-plasma molecular beam epitaxy (MBE) system. The islandlike buffer structure was formed by the repetition of the thin LT GaN layer deposition and annealing process. From the measurement of the surface morphology at the initial stage of the growth on this buffer structure, it is found that the coalescence in the initial growth stage occurred mainly between islands on the same step surface of the substrate. The surface morphology of the grown GaN layer had a flat steplike feature. The X-ray diffraction (XRD) analysis of a 2.5-µm-thick GaN layer grown on this buffer structure showed a 210 arcsec full width half maximum (FWHM) of the peak in the (0002) ω-rocking curve, and 850 arcsec FWHM in the (10–12) ω-rocking curve.

High Breakdown Voltage AlGaN/GaN MIS-HEMT with SiN and TiO/sub 2/ Gate Insulator

We report the fabrication of AlGaN/GaN high electron mobility transistor (HEMT) with high breakdown voltage by employing the metal-insulator-semiconductor (MIS) gate structure. SiO 2 , SiN, and TiO 2 were used for the insulators. The gate leak current was significantly reduced by employing the MIS structure, and the breakdown voltage characteristics were improved. The breakdown voltage of the MIS-HEMTs increased non-linearly with the increase of gate-drain length L gd . The TiO 2 insulator exhibited highest breakdown voltage of 2 kV with the on-resistance of 15.6 mΩ cm 2 .for L gd = 28 μm. On the other hand, the breakdown voltage and on-resistance for SiN MIS-HEMT were found to be 1.7 kV and 6.9 mΩ cm 2 , respectively. We demonstrated that AlGaN/GaN MIS-HEMTs are promising not only for high speed applications but also for high power switching applications.

Reduction of current collapse in AlGaN/GaN HEMTs using thick GaN cap layer

1 Department of Electrical Engineering, Faculty of Science and Technology, Tokyo University of Science. 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan Advanced Power Electronics Center, AIST, Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8568, Japan +Phone +81-29-861-5647 E-mail: mitsu.shimizu@asit.go.jp Leading Edge Technology Development Department, Taiyo Nippon Sanso Corporation, 10 Okubo, Tsukuba, Ibaraki 300-2611, Japan