GaN/AlxGa1-xN heterostructures were grown by metal-organic vapor phase epitaxy (MOVPE) to study in detail the formation of two-dimensional hole gases (2DHG). In contrast to the common double-heterostructure approach to create 2DHG, which is based on GaN buffer layers and leads to the parallel formation of a two-dimensional electron gas (2DEG), this concept is designed to create a 2DHG only. The Al mole fraction in the AlGaN buffer and the GaN channel thickness are each varied to investigate their influence on 2DHG properties. The carrier concentrations as determined by room temperature Hall measurements follow the expected trend given by the Al content dependence of the spontaneous polarization of the relaxed AlGaN buffer. A 2DHG density as high as of 1.6·1013 cm-2 with a negligible dependence on temperature (80 – 300 K) is determined for a GaN/Al0.29Ga0.71N heterostructure by temperature-dependent Hall measurements. Higher carrier concentrations can also be achieved, yet strain relaxation of the GaN channel degrades the transport properties for Al contents above 30 %.

The ability to monitor temperature variations during the actual operation of power modules is key to reliability investigations and the development of lifetime prediction strategies. This paper proposes an original solution, specifically devised with novel fast-switching silicon carbide (SiC) power MOSFETs in mind. The results show ability to track temperature variations resulting from active power cycling of the devices, including high speed transients, thus enabling to discriminate among different potential failure mechanisms. Validation of the proposed methodology and its accuracy is carried out with the support of infrared thermography.

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We report on p-channel metal-insulatorsemiconductor heterostructure field-effect transistors (MISHFET) based on p-GaN/uid-GaN/Al0.29Ga0.71N single heterostructures on sapphire substrates, grown by metalorganic vapor phase epitaxy (MOVPE). The impact of p-GaN layer removal and channel layer thickness adjustment by dry-etching on the characteristics of the MISHFET are investigated. Depending on the remaining GaN thickness (tGaN), the fabricated MISHFET show either depletion-mode (d-mode) operation with a threshold voltage Vth of 3.8 V and an on-current |ID,on| of 9.5 mA/mm (tGaN = 21 nm) or enhancement-mode (e-mode) operation with Vth of -2.3 V and |ID,on| of 1.5 mA/mm (tGaN = 12 nm). Independent of the etching depth, all devices exhibit a very low off-state drain current |ID,off|~10 -8 mA/mm and a steep subthreshold swing (SS) between 80 and 89 mV/dec. Similar to n-channel devices, a Vth instability caused by charge trapping at the dielectric/semiconductor interface is found, emphasizing that careful interface engineering is required for good device performance.