Performance of H-diamond MOSFETs with high temperature ALD grown HfO2 dielectric

Abstract

Hydrogen-terminated diamond (H-diamond) metal-oxide-semiconductor field effect transistors (MOSFETs) with different structures were fabricated on the same polycrystalline diamond plate and their performances were compared. A 28-nm-thick HfO2 layer grown at 300 °C by atomic layer deposition (ALD) system was used as both gate dielectric and passivation layer. Devices A and B have the same source-to-drain distance of 6 μm but different gate lengths of 2 μm (device A) and 6 μm (device B), and in device B the gate extends over the source/drain electrodes with the HfO2 film separating them. Device C has a similar structure with device A but a larger gate length (6 μm). Among these devices, device A shows the highest saturation drain current of 190.6 mA/mm at VGS = −8 V, and device B shows the lowest on-resistance of 61.61 Ω·mm. All the devices show a high on/off ratio of about 109 and a gate leakage current lower than 10−10 A. It is also extracted a constant carrier mobility of 37.1 cm2/Vs in the gated channel in a large VGS range of −2 V ≤ VGS ≤ −8 V, which indicates the good interface characteristics between H-diamond and HfO2 and contributes to the high device performances. These results indicate that high conductivity 2DHG and high performance MOSFET devices can also be achieved by depositing high temperature grown HfO2 on the H-diamond surface.