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We first report on the thermal stability and electrical properties of 5 nm-thick TaN films prepared by atomic layer deposition (ALD) using pentakis(ethylmethylamino)tantalum (PEMAT) and ammonia. The deposition rate of the ALD-TaN process was about ∼0.067 nm per cycle in a temperature range between 200 and 250 °C, which is a typical feature of ALD process. In cross sectional transmission electron microscopy (TEM) images, the deposited TaN films exhibited a very smooth and uniform interface. The thermal stabilities of these films were tested by depositing a Cu film of 200 nm thickness on a TaN layer and subsequently performing annealing for 30 min by varying the temperature from 300 to 800 °C in N2 ambient. The high and low-frequency capacitance–voltage (C–V) and breakdown characteristics of a Cu/TaN/SiO2/Si capacitor showed that the barrier properties of thin TaN films against Cu diffusion are inhibited above 500 °C, which is considerably lower than the inhibition temperature estimated by four-point probe or X-ray diffraction (XRD) measurement.

We present the electrical characteristics of an AlGaN/GaN/p-GaN heterostructure field-effect transistor (HFET) with a Si delta-doped layer. The p-GaN layer greatly improves buffer isolation (between neighboring mesas) in the AlGaN/GaN HFET and leads to effective carrier confinement. The Si delta-doped layer compensates not only the carrier depletion caused by the formation of a pn junction, but also even causes an increase in two-dimensional electron gas (2DEG) density. The proposed AlGaN/GaN HFET shows greatly improved electrical characteristics such as high drain current density and transconductance and low buffer and gate leakage currents compared with those of conventional AlGaN/GaN HFETs.