Determination of the Thickness of Nanometer-Thick β-Ga ₂ O ₃ Membranes from Optical Interference and Colorimetric Analysis for Applications in Next-Generation Semiconductors

High Resolution Image Download MS PowerPoint Slide β-phase gallium oxide is emerging as a next-generation semiconductor material due to its ultrawide bandgap, high breakdown voltage, capabilities as a solar-blind ultraviolet photodetector, and resistance to extreme conditions. β-Ga 2 O 3 membranes are available in various thicknesses and can be characterized by using standard techniques, e.g., atomic force microscopy (AFM). In this work, the use of optical interference patterns is demonstrated as an alternative characterization technique, highlighting its noncontact, user-friendly, and high-throughput thickness assessment for submicron-thick β-Ga 2 O 3 membranes. Thicknesses of (100) β-Ga 2 O 3 membranes on 290 nm SiO 2 /Si substrates are determined by applying Fresnel’s law to fit the contrast profile via optical interference patterns, while accuracy is assessed by atomic force microscopy. Moreover, the color map, calculated to assign the observed color of the membranes to their thickness, shows excellent agreement with the experimental results. The color-to-thickness correspondence is not always univocal and shows repeating color trends over thickness. Membranes of lesser thickness display colors of red, green, and pink, whereas membranes exceeding 600 nm predominantly exhibit orange and yellow tones. Finally, total color differences (TCD) analysis illustrates that (100) β-Ga 2 O 3 membranes on 129, 221, 310, 392, and 467 nm SiO 2 /Si substrates have the best contrast; thus, membranes are more distinguishable.