AlGaN/GaN HEMTS: material, processing, and characterization

• Published in: Journal of materials science. Materials in electronics Vol. 14; no. 5-7; pp. 271 - 277
• Main Authors: CALLE, F, PALACIOS, T, MONROY, E, GRAJAL, J, VERDU, M, BOUGRIOUA, Z, MOERMAN, I
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Norwell, MA Springer 01-05-2003; Springer Nature B.V; Springer Verlag
• Subjects: Aluminum gallium nitrides; Applied sciences; Devices; Electronics; Exact sciences and technology; Gallium nitrides; Gates; High electron mobility transistors; Lithography; Microelectronic fabrication (materials and surfaces technology); Physics; Semiconductor devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transistors; Ternary compound; Binary compound; Output power; Electron beam lithography; Dry process; Aluminium nitride; Gallium nitride; Dislocation density; High electron mobility transistor; Microelectronic fabrication; MOVPE method; Drain current; Ion beam etching; Photolithography; Transconductance; Electrical characteristic; Passivation
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1023/A:1023951323307

The growth of AlGaN/GaN high electron mobility transistor (HEMT) structures on sapphire by metal organic vapor phase epitaxy (MOVPE) is described, with special emphasis on procedures to reduce dislocation density. All the processing steps involved in the fabrication of nitride-based HEMTs have been optimized, including dry etching by ion beam milling, evaporation of Pt/Ti/Au gate contacts, and SiN^sub x^ surface passivation. Devices with several gate lengths and different geometries have been fabricated by standard photo- and e-beam lithography. d.c. drain current and transconductance increase when gate length is reduced, up to 950 mA mm^sup -1^ and 230 mS mm^sup -1^, respectively, at V^sub GS^=0 V, in HEMTs with a gate length L^sub G^=0.2 μm. A maximum output power higher than 5 W mm^sup -1^ is estimated. Finally, small-signal measurements yield f^sub T^=12 GHz and f^sub max^=25 GHz for HEMTs with L^sub G^=0.5 μm, which increase up to 20 and 35 GHz for L^sub G^=0.2 μm, respectively. Limitation of high-frequency performance by parasitics is discussed.[PUBLICATION ABSTRACT]