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 Freescale´s 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 T_CHANNEL = 150degC of 20 years of operation at a 1 ppm degradation level by a wide margin.