Karen E. Moore

A GaN HFET Device Technology on 3" SiC Substrates for Wireless Infrastructure Applications

This report presents a GaN HFET technology for wireless infrastructure applications. Using an optimized process, low DC-RF dispersion is seen via pulsed I-V measurements. At a drain bias of 48 V and frequency of 2.14 GHz, devices with 0.3 mm gate periphery produce 10-11 W/mm with associated PAEs in the range of 62-67%. Devices with 12.6 mm gate widths produce a saturated output power of 74 W (5.9 W/mm) with an associated power-added efficiency (PAE) of 55%. Under single-carrier W-CDMA conditions, an output power of approximately 10 W and 27% associated power-added efficiency (PAE) is realized at an ACPR of -40 dBc

GaN RF device technology and applications, present and future

Over the last decade, Gallium Nitride (GaN) has emerged as a mainstream RF technology with disruptive performance potential. Here, we present GaN technology in the context of current commercial RF communications applications as well as future applications. We show state of the art >200W, >75% efficient packaged device performance at 2.14 GHz using a 0.6 μm 48 V technology and apply the device technology to a 400 W ultra-small footprint Doherty power amplifier. We also describe extending the 0.6 μm technology to a 0.2 μm gate length that allows for higher fT that will enable future technology for high-efficiency switch-mode amplifiers.

Characterization and thermal analysis of a 48 V GaN HFET device technology for wireless infrastructure applications

This report presents the DC, pulsed I–V, small signal, and large signal characteristics of Freescale’s 48 V GaN HFET technology. Characterization of large signal performance for a 12.6 mm at 48V drain bias shows 89 W output power with an associated power density of 7.1 W/mm, linear gain of 17.5 dB, and a power-added efficiency (PAE) of 62%. Analysis of channel temperature over drain bias shows that the maximum channel temperatures at 28 V and 48 V are 107 °C and 245 °C, respectively during saturated RF operation. Data for RF drift over time on a 16.2 mm device show less than 0.2 dB of RF drift for ≫1000 hrs. of testing. This level of RF performance represents a significant ≫4 dB gain and ≫2 W/mm power density improvement over Freescale’s previously reported GaN HFET technology.

High Gain, High Efficiency 12V pHEMT Power Transistors for WiMAX Applications

The combination of Freescales production pHEMT process with a self-aligned field plate, creates a device technology that delivers high gain and efficiency while meeting WiMAX linearity requirements. Compared to the standard production process, field plate devices show gain improvement of about 3 dB while other important device parameters such as power density, linearity, and efficiency are maintained. To demonstrate the improved performance of the field plate technology, three devices with total gate width of 7.2 mm, 14.4 mm, and 25.2 mm were designed and evaluated using a 64 QAM OFDM signal at 3.55 GHz. The devices delivered power of 28.5 dBm, 31.2 dBm, and 33 dBm, respectively, while meeting an EVM linearity requirement of 3%.

Intrinsic Reliability of a 12 volt Field Plate pHEMT Measured using Conventional and Step Stress Methods

High voltage 12 volt GaAs-based pHEMT devices are a commercial work horse for higher frequency infrastructure applications, including cable television, cellular base stations, and, potentially, WiMAXtrade. For the device described here a self-aligned field plate was integrated into Freescales production 12 volt pHEMT process to achieve high breakdown (> 30 volt) and high gain for 3.55 GHz operation. The reliability of this 12 volt field plate pHEMT device was evaluated using both a conventional three temperature DC accelerated stress test and a series of temperature step stress tests at a current stress level of 70 mA/mm. The current acceleration factor was measured and then used to predict the reliability at the actual device use condition of 30 mA/mm. For the targeted infrastructure applications the 12 volt field plate pHEMT device exceeds the reliability target at TCHANNEL = 150degC of 20 years of operation at a 1 ppm degradation level by a wide margin.