14 June 2012

Cree unveils 0.25µm, 40V and 0.4µm, 50V GaN-on-SiC RF MMIC foundry processes

Cree Inc of Durham, NC, USA has announced the qualification and production release of two new gallium nitride (GaN) processes: G40V4 (a 0.25µm process with operating drain voltage up to 40V) and G50V3 (a 0.4µm process with operating drain voltage up to 50V). The increased operating voltage and RF power density of the new processes enable smaller die and more compact, higher-efficiency amplifiers than possible with conventional technologies. Both technologies are compatible with Cree’s proven GaN monolithic microwave integrated circuit (MMIC) technology on 100mm-diameter silicon carbide (SiC) wafers with a full complement of passive circuit elements and nonlinear models.

The new processes are now available for development and full-rate production. Cree says that, with these processes, it offers numerous foundry service options to facilitate the rapid development of custom circuits, including full and dedicated mask sets.

The G40V4 process has been qualified at both 28V and 40V operation with RF power densities up to 6W/mm of FET periphery with operation up to 18GHz. The G50V3 process has been qualified for 50V operation and RF power densities up to 8W/mm with operation through 6GHz.

Both of these processes are derivatives of Cree’s previously released G28V3 28V, 0.4µm process that has been in production since 2006 and exhibits what is claimed to be one of the lowest field failure rates of any microwave technology in the industry (a Failure in Time rate of nine device failures per billion hours of operation).

Cree estimates that for a typical three-sector, multi-band LTE/4G telecom remote radio head (RRH) installation, simply switching to GaN from conventional transistor technology could reduce RRH power consumption by up to 20%, translating directly into lower operating costs and reduced energy consumption. Beyond operational cost savings, there can also be a significant saving in the initial cost of the system. GaN’s benefits of higher voltage and higher efficiency allow smaller heat sinks and enclosures, less complex RF amplifiers and lower-cost AC-to-DC and DC-to-DC converters. Systems that previously required large fans for cooling can now be air cooled. All of these improvements can reduce the system bill of material cost by up to 10%, resulting in significantly lower system acquisition costs, Cree reckons.

Similar benefits are seen for military radar systems, where the improved efficiency from Cree’s GaN processes can not only reduce operational power consumption but also improve system life-cycle cost via reduced maintenance. The G40V4 and G50V3 processes can operate at a junction (channel) temperature of 225°C with a median life-time of more than 2 million hours (228 years). This reliability can dramatically lower the cost of radar system repair and upkeep over its operating life, claims Cree.

“Our customers have been asking for a reliable, higher-frequency process to exploit the advantages of GaN for applications greater than 6GHz, including satcom, radar and electronic warfare markets, and we believe our new G40V4 process successfully satisfies their needs,” says Jim Milligan, director of RF & microwave. “To address our customers’ need for lower-cost GaN solutions, the 50V operating voltage of our new G50V3 process has been specifically engineered to provide an extremely low price in terms of dollars per watt of RF output power,” he adds. “The cost-performance of our G50V3 process is designed to rapidly accelerate the adoption of GaN in extremely cost-sensitive markets such as telecom infrastructure, where GaN can now provide performance advantages not realizable in silicon LDMOS,” he continues.

“The higher operating voltage and higher efficiency possible with these new processes are key to rapid adoption,” says Dr Cengiz Balkas, VP & general manager power and RF, Cree. "Switching to GaN for upcoming LTE/4G macro-cell base-stations could save telecom operators over $2bn annually in reduced energy costs,” he reckons. “Fortunately, the telecom industry is beginning to recognize these potential savings. “Cree is aiming to deliver more than 75 million watts of GaN transistors into telecom base-stations this calendar year.

At 40V operation, Cree’s G40V4 process exhibits up to 6W/mm Psat (saturated output power) at 18GHz. Typical device characteristics at 10GHz are 65% power-added efficiency (PAE) and 12dB of small signal gain. At 50V operation, the G50V3 process demonstrates up to 8W/mm Psat at 6GHz. Typical device performance at 3.5GHz is 70% PAE with 12dB of small-signal gain. Both GaN processes are qualified for maximum operating channel temperature of 225°C with a median time to failure (MTTF) of greater than 2 million hours.

In addition, Cree is releasing MMIC design kits with proprietary scalable nonlinear high-electron-mobility transistor (HEMT) models suitable for operation with Agilent’s Advanced Design System (ADS) and AWR’s Microwave Office simulator platforms. The design kits also contain a full suite of passive components - resistors, capacitors, spiral inductors and substrate ground vias that can be used to simulate full MMIC performance and provide significantly reduced design cycle times.

The Cree RF team will be present in booth 2125 at the 2012 IEEE MTT-S International Microwave Symposium (IMS) in Montreal, Canada (17-22 June).

Tags: Cree GaN-on-SiC RF MMIC

Visit: www.cree.com/rf

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