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New concepts for normally-off power Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT)

Saleem Hamady 1
1 LAAS-ISGE - Équipe Intégration de Systèmes de Gestion de l'Énergie
LAAS - Laboratoire d'analyse et d'architecture des systèmes
Abstract : AlGaN/GaN HEMTs are very promising candidates for high frequency applications with high power and low noise. While switching applications strongly demand normally-off operation, conventional HEMTs attain a channel populated with electrons at zero gate voltage making them normally-on. For the sake of achieving normally-off HEMTs, several structures have been proposed such as recessed gate structures, fluorine ion treatment, pn junction gate structures, thin AlGaN barrier and Gate Injection transistor. The effectiveness of the agent used to obtain normally-off, whether it is recessing the gate, introducing a cap layer or implanting fluorine, increases as the agent comes closer to the AlGaN/GaN interface. Unfortunately, when introducing a cap layer or recessing the gate, coming closer to the interface means decreasing the barrier thickness, which strongly affects the density of the 2DEG. In the case of fluorine implantation, getting closer will increase the probability of fluorine ions getting into the channel and hence degrade the mobility of the 2DEG. In this work we propose two new concepts to achieve normally-off operation. We suggest the introduction of negative fluorine ions on one hand or a p-GaN region on the other hand, below the channel, under the AlGaN/GaN interface and away from high current density regions. After calibrating the simulator using experimental results from a normally-on HEMT device, we have shown that our proposed structures are more effective: the concentration required to achieve normally-off operation is lower than in the other existing solutions and the confinement of the two dimensional electron gas below the gate is better. The proposed ideas were also applied to Metal Insulator Semiconductor HEMT (MIS-HEMT) and Gate Injection Transistor (GIT), giving rise to a normally-off HEMT with high controllable threshold voltage.
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Contributor : Arlette Evrard <>
Submitted on : Tuesday, March 17, 2015 - 2:57:17 PM
Last modification on : Thursday, June 10, 2021 - 3:02:26 AM
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  • HAL Id : tel-01132563, version 1


Saleem Hamady. New concepts for normally-off power Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT). Micro and nanotechnologies/Microelectronics. Universite Toulouse III Paul Sabatier, 2014. English. ⟨tel-01132563⟩



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