Bruce M. Green

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.

AlGaN/GaN HEMT TCAD simulation and model extraction for RF applications

GaN devices have significant advantages in power density, thermal characteristics, and voltage range over those based on conventional compound semiconductors or Silicon. With GaN, as in other materials systems there are significant advantages in cycle time and strength of design from use of TCAD. Here TCAD simulations of AlGaN/GaN HEMTs are shown to accurately match measured DC and small signal AC data. For large signal RF applications it is necessary to use modeling to extend the application of this TCAD solution. Proprietary models are extracted from TCAD data and demonstrated.

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.

Reduction of Low-Temperature Nonlinearities in Pseudomorphic AlGaAs/InGaAs HEMTs Due to Si-Related DX Centers

The linearity of conventional pseudomorphic AlGaAs/InGaAs/AlGaAs high-electron mobility transistors with planar doping in the AlGaAs layers is shown to degrade at low temperatures down to -40°C, as measured by the adjacent-channel power ratio under wideband code-division multiple-access modulation. A modified structure, in which the planar Si doping layers are placed within thin single GaAs quantum wells inside the AlGaAs barrier layers, eliminates this degradation. Deep-level transient spectroscopy and persistent photocapacitance measurements show that trapping on DX centers is effectively eliminated. The linearity improvements are therefore attributed to the elimination of this trapping. Self-consistent solutions of the Schro¿dinger and Poisson equations show that the transfer of the donor electrons into the channel is essentially the same in the modified and conventional structures.