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We present GaN-based high electron mobility transistors (HEMTs) with a 2-nm-thin InAlN/AlN barrier capped with highly doped n(++) GaN. Selective etching of the cap layer results in a well-controllable ultrathin barrier enhancement-mode device with a threshold voltage of +0.7 V. The n(++) GaN layer provides a 290-Omega/square sheet resistance in the HEMT access region and eliminates current dispersion measured by pulsed IV without requiring additional surface passivation. Devices with a gate length of 0.5-mu m exhibit maximum drain current of 800 mA/mm, maximum transconductance of 400 mS/mm, and current cutoff frequency f(T) of 33.7 GHz. In addition, we demonstrate depletion-mode devices on the same wafer, opening up perspectives for reproducible high-performance InAlN-based digital integrated circuits.

Since the middle of the 90's, GaN epitaxy techniques have been developed, using either MOCVD or MBE growth methods. A low cost approach is presented aiming at satisfying thermal issues encountered on conventional substrates such as SiC, Sapphire and more recently Silicon. Domain of application are being covered with their associated challenges: RF and High Power applications. Stress engineering is one of the key parameters.

AlGaN/GaN high electron mobility transistors (HEMTs) with Si and Al 2 O 3 substrates reveals anomalies on I ds – V ds – T and I gs – V gs – T characteristics (degradation in drain current, kink effect, barrier height fluctuations, etc.). Stress and random telegraph signal (RTS) measurements prove the presence of trap centers responsible for drain current degradation. An explanation of the trapping mechanism responsible for current instabilities is proposed. Deep defects analysis performed by capacitance transient spectroscopy ( C -DLTS), frequency dispersion of the output conductance ( G ds ( f )), respectively, on gate/source and drain/source contacts and RTS prove the presence of deep defects localized, respectively, in the gate and in the channel regions. Defects detected by C -DLTS and G ds ( f ) are strongly correlated, respectively, to barrier height inhomogeneities and kink anomalies. Gate current analysis confirms the presence of ( G – R ) centers acting like traps at the interface GaN/AlGaN. Finally, the localization of these traps defects is proposed.

DC and RF measurements of an emerging AIInN/GaN high electron mobility transistor (HEMT) technology for power performances are reported. High electron transport properties in this structure attributed to the material quality are demonstrated. Indeed, in spite of a basic technology which provides high access resistances, high frequency performances with a cutoff and maximum oscillation frequencies about 26 and 40 GHz, respectively, at V-DS = 10 V were achieved. A maximum drain current density more than 1.3 A/mm with a pinch-off breakdown voltage about 40 V without any passivation was obtained. These results show that this device is very promising for high power performances at high frequency.