Interfacial engineering of InGaAs/high-k metal-oxide-semiconductor field effect transistors (MOSFETs)

The electrical properties of In_xGa_1-xAs (x=0.53, x=0.65) MOSFETs have been studied for three different ex-situ surface passivation techniques (HF clean, (NH₄)₂S clean and PECVD a-Si interlayer) with HfO₂ gate dielectric (4 nm and 8 nm) and Ni/Au gate metal. In_0.65Ga_0.35As devices demonstrate much higher drive current than In_0.53Ga_0.47As devices. Devices with an a-Si IPL exhibit the highest drive current and mobility, whereas (NH₄)₂S surface cleaned devices show higher drive current, trans-conductance and mobility compared to HF cleaned devices. Also devices with a-Si IPL and (NH₄)₂S clean shows the highest and the lowest sub-threshold swing, respectively. Furthermore charge pumping measurements show a similar average mid-gap D_it indicating that mid-gap D_it is not related to the improvement in transport characteristics.