MOVPE growth and characterization of AlPN layers for HFETs

The growth of AlPN layers by metalorganic vapor phase epitaxy (MOVPE) and their use as barrier layers on GaN buffer layers for heterojunction field effect transistors (HFETs) was investigated. Quantitative energy-dispersive X-ray spectroscopy (EDX), wavelength-dispersive X-ray spectroscopy (WDX), and X-ray photoelectron spectroscopy (XPS) measurements were used to determine the atomic P content of the AlPN layers. PH3 and tertiarybutyl phosphine (tBP) proved to be very similar P precursors for the MOVPE growth of AlPN layers. The AlPN HFET epitaxial layer structures were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), Hall effect, conductivity, and capacitance–voltage (CV) measurements. AlPN/AlN/GaN/sapphire HFET devices were fabricated and characterized. The results indicate that AlPN, similar to Ga1-xPxN, suffers from a preferential incorporation of P onto the group III lattice site instead of the desired N site, and may therefore not allow for downscaling of HFET devices as predicted for the lattice changes when incorporating P at N sites.