Robert Joseph Therrien

AlGaN/GaN HFETs fabricated on 100-mm GaN on silicon (1 1 1) substrates

Abstract The group III-nitride material system has been demonstrated by many groups to produce high performance, heterostructure field effect transistors (HFETs). AlGaN/GaN heterostructures yield high two-dimensional electron gas densities with high carrier mobilities and simultaneous high breakdown field. Devices based on this structure perform well at high power and at high frequency operating conditions. Most AlGaN/GaN HFETs to date have been produced on sapphire or silicon carbide substrates due to the limited availability of bulk GaN substrates. There are limitations in using these substrate materials in either thermal conductivity, cost or wafer diameter. The use of silicon substrates can overcome the issues of sapphire and SiC that limit manufacturability. In this work, results from HFETs fabricated on 100-mm silicon substrates using a proprietary MOCVD reactor design will be presented. The quality and uniformity of the GaN epitaxy, the microwave characterization of these devices at 2 GHz, and the thermal performance of large periphery devices on this material will be detailed. The electrical performance of these devices is found to be comparable to that of early devices on sapphire and SiC. The results will illustrate the viability of silicon as a low cost, manufacturable platform for AlGaN based devices from the standpoint of epitaxy, device performance, and thermal power handling.

150 W GaN-on-Si RF power transistor

A large periphery high power AlGaN/GaN HFET grown on a silicon substrate has demonstrated over 150 W of CW RF output power along with excellent drain efficiency of 65%. When operated under WCDMA modulation and 28 Vdc drain supply voltage, these devices produced 20 W of RF output power with a corresponding drain efficiency of 27% while achieving an adjacent channel power ratio (ACPR) of -39 dBc. A 36 mm device was tested in a DPD linearizer under multi-carrier WCDMA modulation and achieved 20 dB of linearity improvement with 35% drain efficiency. Lastly, device reliability data is presented and shows extrapolated 20 year drift estimates of less than 1 dB for Psat. Index Terms - AlGaN/GaN HFETs, GaN high electron mobility transistor (HEMTs), linearity, reliability, RF power transistors.

Performance of AlGaN/GaN HFETs fabricated on 100 mm silicon substrates for wireless basestation applications

Third generation wireless communications standards such as W-CDMA place challenging requirements on microwave power transistors. To date, these challenges have been addressed with two primary technologies, Si LDMOS FETs and GaAs FETs. A new technology (AlGaN/GaN HFET) that shows the potential for addressing these strict system requirements is now becoming available. The growth and fabrication of GaN-based HFETs on a manufacturable 100 mm silicon platform are discussed. Results from 36 mm GaN HFETs are reported with particular attention to their ability to address the needs of the W-CDMA base transceiver station output power stage, demonstrating in excess of 15 W output power at W-CDMA operation with -39 dBc ACPR and 29% drain efficiency. Results of initial high-temperature operating life testing are presented, showing excellent device stability at a junction temperature of 200/spl deg/C, and predicting about 10% drift in DC parameters and less than 1 dB in output power over a 20-year life.

A Comparison of AlGaN/GaN HFETs on Si Substrates in Ceramic Air Cavity and Plastic Overmold Packages

AlGaN/GaN HFETs on Si substrates have been assembled in ceramic air cavity and plastic overmold packages. Thermal, DC, small and large signal RF and reliability characterization have been performed on both types of devices. Thermal characterization shows that the thermal resistance of the plastic overmolded parts is higher resulting in higher operating temperatures. The higher operating temperature causes parameters such as the peak CW power to be lower than that seen in the ceramic air cavity package. The advantage of the plastic packaging resides in its >10x lower package assembly cost.

AlGaN/GaN HFETs on Si Substrates for WiMAX Applications

AlGaN/GaN HFETs on Si substrates are tested under OFDM modulations and show excellent performance from 3.3GHz to 3.8GHz. Performance on an 8mm device (NPT35010) in power small outline package (PSOP2) shows 1.5W output power, 11.2dB gain, 28.6% drain efficiency and 2% EVM at 3.5GHz. Large periphery 36mm devices were mounted in ceramic packages (NPT35050) and showed greater than 7W output power, > 11dB gain, 27.2% drain efficiency and 2% EVM at 3.5 GHz. Additionally data was taken across process from 23 devices and 5 process lots to demonstrate repeatability. Finally the same RF data was collected over flange temperature from -40degC to +85degC and demonstrated stable performance over temperature. These results demonstrate the potential for GaN-on-Si HEMTs for use in WiMAX applications