Effect of AlN and AlGaN Interlayers on AlScN/GaN Heterostructures Grown by Metal-Organic Chemical Vapor Deposition

AlScN/GaN heterostructures with their high sheet carrier density (ns) in the two-dimensional electron gas (2DEG) have a high potential for high-frequency and high-power electronics. The abruptness of the heterointerface plays a key role in the 2DEG confinement, and the presence of interlayers (AlN, AlGaN) affects ns and electron mobility (mu) and determines the sheet resistance (Rsh). AlScN/GaN heterostructures suitable for high-electron mobility transistors (HEMT) with and without a nominal AlN interlayer were grown by metal-organic chemical vapor deposition (MOCVD) and characterized electrically and structurally to gain a systematic insight into the unintentional formation and control of graded AlGaN interlayers by diffusion of atoms at the heterointerface. The AlN interlayer increases ns from 2.52 x 1013 cm-2 to 3.25 x 1013 cm-2 and, as calculated by one-dimensional Schro''dinger-Poisson simulations, improves the 2DEG confinement. The barrier growth temperature was varied from 900 degrees C to 1200 degrees C to investigate the effect of the thermal budget on diffusion. Growth at 900 degrees C reduces the thickness of the graded AlGaN interlayer and improves the 2DEG confinement, leading to Rsh of 211 omega/sq, ns of 2.98 x 1013 cm-2, and mu of 998 cm2/(Vs).

Automated summary

In this study, AlScN/GaN heterostructures were grown and characterized to investigate the effect of diffusion of AlGaN on 2DEG confinement. The presence of interlayers and the growth temperature were found to significantly affect the sheet carrier density and electron mobility.