High-Quality AlGaN/GaN HEMTs Growth on Silicon Using Al_0.07Ga_0.93N as Interlayer for High RF Applications

In this study, AlGaN/GaN high electron mobility transistor (HEMT) with different interlayer thicknesses of Al_0.07Ga_0.93N were grown by metal-organic chemical vapour deposition (MOCVD) is investigated. The AlGaN/GaN HEMTs have the same device’s structure, with the Al_0.07Ga_0.93N interlayer thickness varied from 0 to 800 nm. All of the samples demonstrate high crystal quality in the GaN channel, with low dislocation density of (1.34-3.81) × 10⁹ cm⁻² and low AFM surface roughness of 0.27-0.39 nm. The heterostructure with an interlayer exhibits better mobility (1750 cm² V∙s⁻¹) compared to the structure without an interlayer (1610 cm² V∙s⁻¹). Furthermore, the interlayer improves breakdown voltage, and reduces insertion loss. The DC characteristics show that the 300 nm-thick Al_0.07Ga_0.93N is beneficial in improving leakage current and iso-breakdown voltage up to 450 V at a spacing of 10 μm. The insertion loss reduces to -0.75 dB mm⁻¹ compared to the structure without an interlayer. The device with a 300 nm-thick Al_0.07Ga_0.93N interlayer exhibits the potential of RF, including a measured transconductance of 440 mS∙mm⁻¹ and cutoff frequencies of f T / f max = 48/96 GHz at a given bias point.