Thermally desorbed InN capping layers for nitride surface science

Group III-nitride thin films grown by molecular beam epitaxy are essential for optoelectronic and power devices, where surface and interface quality critically influence performance. However, transferring films for processing or characterization introduces contamination from atmospheric exposure, complicating surface analyses. To address this limitation, we establish the use of InN capping layers to protect the film surface. We demonstrate the procedure by discussing synchrotron X-ray characterization of high Al-content AlGaN grown films with different strain states that are decapped under vacuum at the Advanced Photon Source. Exploiting the lower decomposition temperature of InN (~450 °C) relative to AlGaN (>800 °C), we thermally desorb the cap under vacuum to expose the pristine AlGaN film surface. RHEED patterns collected before and after capping confirm that InN deposition and desorption leave the AlGaN surface unaltered. This work serves as a proof of concept for the use of InN capping as an effective, reversible protection method for oxidation-sensitive thin films.