Summary:

Au cours des dernières décennies, des progrès remarquables ont été réalisés sur les transistors à haute mobilité électronique à base de GaN (HEMTs GaN) destinés aux applications d’amplification et de commutation de puissance à haute fréquence. Actuellement, les HEMTs GaN les plus matures sont basés sur des hétérostructures AlGaN/GaN. Plus récemment, les hétérostructures à barrières ultrafines (<10 nm) (in)(ga)alngan riches en al ont également présentées beaucoup d’intérêt pour les applications gamme d’ondes millimétriques. effet, contrairement aux structures algan gan, barrièresultrafines peuvent fournir une densité d’électrons (2deg) deux fois plus élevée tout offrant un rapport d’aspect important (longueur de grille>Abstract:

Over the last decades, remarkable progress has been made on GaN-based high electron mobility transistors (GaN HEMTs) for high frequency power amplification and switching applications. Currently, the most mature GaN HEMTs are based on AlGaN/GaN heterostructures. More recently, Al-rich (In)(Ga)AlN/GaN ultra-thin barrier heterostructures (<10 nm) have also shown great interest for millimeter-wave applications. Indeed, unlike AlGaN/GaN structures, Al-rich ultrathin barriers can provide twice the electron density (2DEG) while offering a large aspect ratio (gate length/gate-channel distance) even with very short gates below 100 nm. Therefore, Al-rich GaN ultra-thin barrier HEMTs allow to operate at higher frequency in a robust manner. In this context, several research groups have demonstrated a unique combination of higher power and wider bandwidth up to 100 GHz by using GaN transistors compared to other technologies (GaAs or silicon). However, most applications require power amplifiers with very high efficiency combined with proven reliability and increased linearity. The state of the art of GaN HEMTs is limited today to about 50% PAE (Power Added Efficiency) and little work has been reported on the reliability of GaN devices using short gates smaller than 150 nm. Nevertheless, one of the major limitations of modern RF devices is the thermal dissipation. Indeed, the power dissipation improves by 80% when the PAE efficiency increases from 50% to 80%. The objective of this work is to provide a state-of-the-art technology in this field with the development and optimization of sub-150 nm GaN gate transistors for millimeter-wave range applications. In particular, we have optimized the buffer layers while optimizing a sub-5 nm AlN barrier in order to increase the power gain, improve the electron confinement under high electric field and simultaneously reduce the trapping effects. In addition, the development of a power measurement bench at 94 GHz has allowed to demonstrate a state-of-the-art power density at W-band with the fabricated components. This work provides a promising basis for ensuring high (including PAE efficiency) and reliable performance of GaN HEMTs for power amplification in the millimeter-wave range related to future 5G telecommunication, space or military applications. [/av_textblock]