Growth of AlxGa1-xN Thin Films with Controllable Composition and Optical Bandgap on 4H-SiC by Sub-Cycle Incomplete Reaction Plasma Enhanced Atomic Layer Deposition

Abstract

Atomic layer deposition (ALD) offers inherent advantages in the preparation of ultra-thin films, particularly for the growth of nanoscale thin films. However, due to the limitations of the ALD cycle concept, the fabrication of three-component thin films, such as AlGaN, with unequal atomic ratios can result in significant layering, preventing the formation of a uniform layer solid solution. In this article, a sub-cycle incomplete reaction plasma-enhanced atomic layer deposition (SIR-PEALD) process is presented that enables precise adjustment of Al-content from 0% to 100% and allows for control of the bandgap within the range of 4.2–5.8 eV. Furthermore, it is found that the growth mechanisms and characteristics of SIR-PEALD on 4H-SiC closely resemble those of GaN and AlN, with all three exhibiting strong substrate inhibition effects. Additionally, during the ALD growth of AlGaN, surface steps can be filled, resulting in remarkably low film surface roughness of 0.1 nm. By combining HRTEM and EDX, it is demonstrated that the elements in the grown thin film are uniformly distributed, without agglomeration or delamination. The innovative SIR-PEALD pathway may also be applicable to the growth of other ternary- or multicomponent materials and can provide new insights into alloying thin films using ALD.