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8 November 2006


TDI samples 4-inch AlN-based semi-insulating wafers

Technologies and Devices International Inc (TDI) of Silver Spring, MD, USA has made available sample quantities of 100mm (4-inch) diameter AlN-based semi-insulating substrates. TDI introduced the first 2-inch AlN-on-SiC
substrates three years ago followed by 3-inch substrates last year, and announced fabrication of the first prototype 4-inch AlN-based semi-insulating substrate this June.

Proprietary stress control technology and crystal growth equipment developed by TDI allows the deposition of crack-free single-crystal AlN film 10-20µm thick. This is sufficient for reliable insulation and low current leakage to the electrically conductive 100mm (4-inch) silicon carbide substrate.

Hence, as well as having good lattice and thermal match to GaN-based devices, says Vladimir Dmitriev, president and CEO, AlN-on-SiC substrates combine the high thermal conductivity of SiC and the high intrinsic electrical resistivity of AlN for ultrahigh-power AlGaN/GaN devices (including HEMTs and high-frequency power amplifiers for next-generation wireless communications). Future applications also include optoelectronic devices, including high-power lasers, operating in the ultraviolet spectrum region.

Test samples have been shipped to customers. "Results have been positive and very encouraging," says president and CEO Vladimir Dmitriev. "Large-area AlN-based substrates offer important technical and economical benefits. This can lead to dramatic cost reductions for GaN high-electron-mobility transistors and power amplifiers, particularly for base-station applications. New product breakthrough will allow our customers to use existing 4-inch manufacturing lines [standard for GaAs RF ICs], reduce
production cost, and speed up commercialization of GaN devices."

Photo: 2-, 3-, and 4-inch AlN-on-SiC wafers. Thick AlN layers are deposited on electrically conducting SiC substrates by proprietary hydride vapor phase epitaxy (HVPE).