Normally‐off AlGaN/GaN MOSHFET using ALD SiO2 tunnel dielectric and ALD HfO2 charge storage layer for power device application

In this work, we have demonstrated a normally‐off AlGaN/GaN metal‐oxide semiconductor heterojunction field effect transistor (MOSHFET) wherein the enhancement mode operation is enabled by charge storage characteristics within a high‐k layer. By combining ALD SiO2 tunnel dielectric and HfO2 charge trapping layer, up to 7 V of threshold voltage (VT) shift depending on the applied gate pulse amplitude (corresponding ∼ 1.2 × 1013 charges/cm2 stored within the charge storage layer) is obtained. Electrical characteristics such as gate leakage current, transconductance, and off‐state breakdown after programming are similar to the initial device. Retention characteristics show about 20% of charge loss after 20000 s. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)