Influence of the Aln/Gan superlattices buffer thickness on the electrical properties of Algan/Gan HFET on Si substrate

The influence of the total thickness (periods of AlN/GaN SLs) of AlN/GaN superlattices (SLs) buffer on the static electrical properties of AlGaN/GaN HFETs is study for the purpose of improving device's breakdown voltage (BV) and reducing its on-resistance (RON). It is found that for top-GaN layer with a constant thickness of lμm, a proper thickness of AlN/GaN SLs buffer (such as 2.5 μm with 100 period AlN/GaN SLs) could obtain better crystal quality of top-GaN layer as well as more robust devices with more superior performance in all aspects. The most robust HFETs in this work have achieved a specific on-resistance (RON, SP) of 0.68 mΩ-cm² (@ LGD=4μm), a maximum on-state drain current (ID, max) of 430 mA/mm (@ LGD=4μm), an On/Off ratio of 2×10⁸, a BV of 552V at a drain leakage current of lμA/mm (@ LGD=15μm), and a figure-of-merit (FOM=BV²/RON, SP) of 168 MW/cm² (@ LGD=8μm).