Project title: Electrical Degradation Mechanisms of RF Power GaAs PHEMTs
Staff: Anita Villanueva
Sponsor: Mitsubishi Electric, Lucent Technologies Fellowship
GaAs PHEMTs are broadly used in RF power applications for wireless systems. Since these devices typically operate at high power levels and under high-voltage biasing, their electrical reliability is of serious concern. Previous studies have identified several distinct degradation phenomena in these devices (such as impact ionization, electron trapping, and surface corrosion, amongst others), but a complete picture has yet to be formed. Our study is aimed at completing this picture and obtaining a detailed physical understanding of the electrical degradation in these devices, so that we can suggest appropriate solutions to improve electrical reliability.
In our study, we have been carrying out various stressing experiments to investigate the degradation of a set of experimental RF power GaAs PHEMTs (provided by our sponsor, Mitsubishi). Most recently, we have studied the electrical degradation of RF power PHEMTs by means of light-emission measurements performed during bias-stress experiments. We showed that electrical degradation can proceed in a highly non-uniform manner across the width of the device, and we identified the origin of this as a small systematic non-uniformity in the recess geometry that impacts the electric field and the impact ionization rate on the drain of the device. This thus suggested that a close examination of the width distribution of electric field in RF power PHEMTs (and FETs in general) is essential to enhance their long-term reliability.
A. A. Villanueva, J. A. del Alamo, T. Hisaka, K. Hayashi, M. Somerville, "Non-Uniform Degradation Behavior Across Device Width in RF Power GaAs PHEMTs," IEEE International Electron Devices Meeting, December 2005. pp. 803-806.
del Alamo, J.A. and A. S. Villanueva, "Thermal, Electrical and Environmental Reliability of InP HEMTs and GaAs PHEMTs." (Invited) 2004 IEEE International Electron Devices Meeting, San Francisco, CA, December 13-15, 2004, pp. 1019-1022.
A. A. Villanueva, J. A. del Alamo, T. Hisaka, K. Hayashi, "Electrical degradation mechanisms of RF power GaAs PHEMTs," IEEE International Electron Devices Meeting, December 2003. pp. 719-722.
Hisaka, T., Y. Nogami, A. Hasuike, H. Sasaki, N. Yoshida, K. Hayashi, T. Sonoda, A. Villanueva and J. A. del Alamo, "Degradation Mechanisms of PHEMTs under Large Signal Operation." 2003 IEEE GaAs IC Symposium, San Diego, CA, November 9-12, 2003, pp. 67-70.