Post-rapid thermal annealing time-dependent engineering of gallium oxide/gallium nitride heterostructures for enhanced optoelectronic performance

Abstract

This study explores the impact of post-rapid thermal annealing (PRTA) time on the topological, structural, optical, and optoelectronic properties of β-Ga₂O₃/GaN heterostructure films. The films were deposited via electron beam evaporation onto sapphire substrates. This research addresses a notable gap in the existing literature by systematically analyzing the impact of short-duration PRTA, specifically for periods of 5, 10, and 15 min at 900 °C in a nitrogen (N₂) ambient atmosphere. The findings indicate that an intermediate surface roughness of 5.29 nm is achieved for the film subjected to a 10-mins anneal, as demonstrated through atomic force microscopy analysis. Furthermore, ultraviolet–visible–near infrared spectroscopy identified two distinct bandgaps associated with the β-Ga₂O₃ and GaN crystal phases, ranging from 4.61 to 4.47 eV for β-Ga₂O₃ and 3.32–3.40 eV for GaN, although no clear trend is observed relative to PRTA time.

The results indicate that the 10-min PRTA condition produces the most balanced enhancements across several critical metrics, including surface smoothness, crystalline quality, bandgap enhancement, dielectric stability, optical mobility, optical resistivity, plasma frequency, and relaxation time. It is noteworthy that excessive annealing for 15 min introduces structural defects and grain coarsening, leading to deterioration in the films' properties. Conversely, insufficient annealing for only 5 min results in suboptimal characteristics, underscoring the importance of determining an appropriate annealing duration for optimal film quality. These findings suggest that a 10-min PRTA time is ideal for enhancing the optoelectronic performance of β-Ga₂O₃/GaN heterostructure films. This Research contributes valuable insights for the fabrication of high-quality β-Ga₂O₃/GaN-based devices, which are essential for advancing optoelectronic applications such as UV photodetectors, power electronics, and high-frequency RF devices.