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Materials 2012, 5(12), 2498-2520; doi:10.3390/ma5122498

Degradation Mechanisms for GaN and GaAs High Speed Transistors

1 Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611, USA 2 Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611, USA 3 Department of Chemical Engineering, University of Florida, Gainesville, FL 32611, USA
* Author to whom correspondence should be addressed.
Received: 24 October 2012 / Revised: 23 November 2012 / Accepted: 23 November 2012 / Published: 27 November 2012
(This article belongs to the Special Issue Compound Semiconductor Materials)
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We present a review of reliability issues in AlGaN/GaN and AlGaAs/GaAs high electron mobility transistors (HEMTs) as well as Heterojunction Bipolar Transistors (HBTs) in the AlGaAs/GaAs materials systems. Because of the complex nature and multi-faceted operation modes of these devices, reliability studies must go beyond the typical Arrhenius accelerated life tests. We review the electric field driven degradation in devices with different gate metallization, device dimensions, electric field mitigation techniques (such as source field plate), and the effect of device fabrication processes for both DC and RF stress conditions. We summarize the degradation mechanisms that limit the lifetime of these devices. A variety of contact and surface degradation mechanisms have been reported, but differ in the two device technologies: For HEMTs, the layers are thin and relatively lightly doped compared to HBT structures and there is a metal Schottky gate that is directly on the semiconductor. By contrast, the HBT relies on pn junctions for current modulation and has only Ohmic contacts. This leads to different degradation mechanisms for the two types of devices.
Keywords: degradation; stress; aging; HBT; HEMT degradation; stress; aging; HBT; HEMT
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Cheney, D.J.; Douglas, E.A.; Liu, L.; Lo, C.-F.; Gila, B.P.; Ren, F.; Pearton, S.J. Degradation Mechanisms for GaN and GaAs High Speed Transistors. Materials 2012, 5, 2498-2520.

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