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Purpose – The purpose of this paper is to report upon high power, internally matched GaN high electron mobility transistors (HEMTs) at Ku band with 1.5 GHz bandwidth, which employ a simple and cost-effective lossless compensated matching technique. Design/methodology/approach – Two 4 mm gate periphery GaN HEMTs are parallel combined and internally matched with multi-section reactive impedance transformers at the input and output networks. The output matching network is designed at the upper frequency of the design band for a flat power of the circuit, while the input matching network is designed at the upper frequency for a flat gain. Findings – With the reactively compensated matching technique, the internally matched GaN HEMTs exhibit a flat saturated output power of 43.2+0.7 dBm and an average power added efficiency of 15 per cent over 12 to 13.5 GHz. Originality/value – This paper provides useful information for the internally matched GaN HEMTs. [ABSTRACT FROM AUTHOR]

In this letter, we report high-performance enhancement-mode (E-mode) Al2O3/AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) fabricated with high-temperature low-damage gate recess technique. The high-temperature gate recess is implemented by increasing the substrate temperature to 180 °C to enhance the desorption of chlorine-based etching residues during the dry etching of AlGaN barrier. High-crystal-quality Al2O3 gate dielectric was grown by atomic-layer deposition using O3 as the oxygen source to suppress hydrogen-induced weak bonds. The fabricated E-mode MIS-HEMTs exhibit a threshold voltage of 1.6 V, a pulsed drive current of 1.13 A/mm, and very low OFF-state standby power of 6.8 \times 10^\mathrm -8 W/mm at V\mathrm {GS} =0 V and V\mathrm {DS} =30 V. At 4 GHz and in pulse-mode operation, the output power density and power-added efficiency were measured to be 5.76 W/mm and 57%, both of which are the highest for GaN-based E-mode MIS-HEMTs reported to date. [ABSTRACT FROM AUTHOR]

Low-pressure chemical vapor deposition (LPCVD) technique is utilized for SiNx passivation of AlGaN/GaN high-electron-mobility transistors (HEMTs). A robust SiNx/ AlGaN interface featuring high thermal stability and well-ordered crystalline structure is achieved by a processing strategy of “passivation-prior-to-ohmic” in HEMTs fabrication. Effective suppression of surface-trap-induced current collapse and lateral interface leakage current are demonstrated in the LPCVD-SiNx passivated HEMTs, as compared with conventional plasma-enhanced chemical vapor deposition-SiNx passivated ones. Energy dispersive X-ray spectroscopy mapping analysis of SiNx/AlGaN interfaces suggests the interface traps are likely to stem from amorphous oxide/oxynitride interfacial layer. [ABSTRACT FROM AUTHOR]

This letter reports a 0.2-\mum gate AlGaN/GaN high-electron-mobility transistors (HEMTs) on an Si substrate passivated with an AlN/SiNx (4/20 nm) stack layer. The 4-nm-thick AlN was grown by plasma-enhanced atomic-layer-deposition. The AlN/SiNx-passivated HEMTs exhibit a high maximum drain current of 930 mA/mm, an three-terminal OFF-state breakdown voltage (BVDS) of 119 V, and a small threshold voltage shift of 130 mV in a wide drain bias range (VDS=3-24~V). Owing to the additional positive polarization charge in the AlN passivation layer, the access resistance Rs in the GaN-on-Si HEMTs is significantly reduced while maintaining small parasitic gate-drain capacitance Cgd, contributing to a high power-gain cutoff frequency fMAX of 182 GHz and a high Johnson's figure of merit of BVDS\times f\,T of 6.43\times 10^12~V/s simultaneously. The accuracy of the RF performance is verified by a small signal modeling based on measured S-parameters. [ABSTRACT FROM AUTHOR]

In this work, Ti/Al/Ni/Au Ohmic contacts to AlGaN/GaN heterostructures with different Ti/Al relative thicknesses were fabricated and characterized. A contact with Ti/Al relative thickness of 20/180 nm presented non-linear current–voltage response and bumpy surface morphology, while a contact with Ti/Al relative thickness of 20/120 nm demonstrated low contact resistance and flat surface morphology. We verify the existence of two electron transport mechanisms, namely carrier tunnelling and direct link through a TiN conductive pathway, by scanning transmission electron microscopy and corresponding electron dispersive x-ray spectra. Ti/Al relative thickness exerts a decisive influence on the alloy reaction processing. Superfluous Al consumes Ti, thus impeding the formation of low-resistance TiN and N vacancies. As a result, electron transport is restricted by the low-efficiency tunnelling mechanism. At the same time, the consumption of Ni causes damage to its blocking effect and arouses the free diffusion of metal alloys, which should be responsible for the rough surface. [ABSTRACT FROM AUTHOR]