A structural analysis of ultrathin barrier (In)AlN/GaN heterostructures for GaN‐based high‐frequency power electronics

Abstract

Metal-organic chemical vapor deposition (MOCVD) is one of the best growth methods for GaN-based materials as well-known. GaN-based materials with very quality are grown the MOCVD, so we used this growth technique to grow InAlN/ GaN and AlN/GaN heterostructures in this study. The structural and surface properties of ultrathin barrier AlN/GaN and InAlN/GaN heterostructures are studied by X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements. Screw, edge, and total dislocation densities for the grown samples have been calculated by using XRD results. The lowest dislocation density is found to be 1.69 Â 10 8 cm À2 for Sample B with a lattice-matched In 0.17 Al 0.83 N barrier. The crystal quality of the studied samples is determined using (002) symmetric and (102) asymmetric diffractions of the GaN material. In terms of the surface roughness, although reference sample has a lower value as 0.27 nm of root mean square values (RMS), Sample A with 4-nm AlN barrier layer exhibits the highest rough surface as 1.52 nm of RMS. The structural quality of the studied samples is significantly affected by the barrier layer thickness.The obtained structural properties of the samples are very important for potential applications like high-electron mobility transistors (HEMTs).

Low-Resistive Ohmic Contacts in High-Electron-Mobility AlN/GaN Heterostructures by Suppressing the Oxygen Incorporation

“…As a critical path to the application of high-speed and high-power radio frequency (RF) devices, high electron mobility transistors (HEMTs) based on III–V semiconductors have gathered persistently increasing interest in recent years. Due to the high mobility and high carrier density of the two-dimensional electron gas (2DEG) formed at the heterointerface, AlGaN/GaN HEMTs have marched into the millimeter wave domain with cutoff frequencies over 100 GHz. − However, during the device dimensional scaling, the short channel effect causes severe deteriorations of the gate response and hence exacerbates the threshold voltage, saturation current, and so forth. − One of the technically realizable solutions to avoid the short channel effect is to reduce the barrier thickness, which makes the ultrathin-barrier AlN/GaN heterostructure a promising candidate in the high-power and high-frequency field in the terahertz wave range. − With the strongest spontaneous and piezoelectric polarization among the III-nitrides, the AlN/GaN heterostructure possesses the highest 2DEG concentration, along with a considerably high carrier mobility offered by the binary alloyed barrier. Nowadays, the progress of epitaxial optimizations makes it possible to offer very low-sheet-resistance 2DEGs in the ultrathin-barrier AlN/GaN heterostructures, which allows significant improvements in the direct current (DC) and RF performance of AlN/GaN HEMTs. − …”