ALD Growth of Mg_xCa_1–xO on GaN and Its Band Offset Analysis

Abstract

Atomic layer deposition (ALD) processes were developed for growing MgO and CaO on GaN substrates using a home-built ALD reactor with amidinate-based precursors. An optimal deposition condition was then determined to deposit pure Mg x Ca 1−x O by tuning deposition temperature, achieving a high-quality film without carbon and hydroxyl contamination. Band offset analysis was conducted by X-ray photoelectron spectroscopy on Mg x Ca 1−x O/GaN samples with various compositions. Mg 0.25 Ca 0.75 O/GaN demonstrated band alignments between defect-free and fully pinned, while other ratios showed near fully pinned alignments, which agree with the best electrical properties achieved in our previous studies. This result indicates that band offset analysis provides a good aid in understanding part of the electrical and interfacial properties for oxide/semiconductor structures.