MOCVD AlGaN/GaN HFET's Material Optimization and Devices Characterization

Abstract

ABSTRACTAn optimization of growth parameters of AlxGa1*xN/AlN/GaN heterostructure field effect transistors (HFET) grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique on SiC and sapphire substrates with relatively high Al mole fraction in the barrier layer (0.3 < x < 0.5) has been presented. The properties of the two-dimensional electron gas (2DEG) forming at the AlxGa1-xN/GaN heterojunction can be tuned by careful adjustments of AlxGa1-xN barrier layer thickness and Al mole fraction, x. The 2DEG sheet conductivities (μ ns) as high as 2.6 × 1016 V-1s-1 at μ ∼ 2200 cm2/Vs and ns ∼ 1.2 × 1013 cm-2 has been achieved on AlxGa1-xN/AlN/GaN HFET structures on SiC substrate at x = 0.47. HFET devices processed on these structures exhibited improved low field conductivities and DC and high frequency performance. Saturation currents above 1.2 A/mm at 0 V gate bias, transconductance as high as 340 mS/mm at Lg = 0.25 μm and FT × Lg > 20 GHz × μm were demonstrated on HFET structure grown on SiC substrates.