High AlN molar fraction AlGaN and AlGaN/AlN superlattices growth by ultra-high-temperature metalorganic vapor phase epitaxy

We demonstrated the growth of high AlN molar fraction AlGaN single-layers and AlGaN superlattices (SLs) using jet stream gas flow metalorganic vapor phase epitaxy. Successful Ga incorporation was confirmed at 1700 °C in AlGaN single-layer growth while maintaining crystalline quality, indicating coherent growth on AlN. During AlGaN/AlN SLs growth, SLs structures with sharp interfaces and a high average AlN molar fraction of 88.0% were obtained at 1500 °C. Scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed that the compositional distribution in the cross section of the AlGaN/AlN SLs was as expected. Furthermore, the dependence on the input Al/(Al+Ga) ratio clarified that controlling the Al flow rate led to a slight adjustment in the average AlN molar fraction, whereas controlling the Ga flow rate resulted in a substantial adjustment in the average AlN molar fraction. These findings are significant for controlling Ga incorporation during the high-temperature AlGaN growth.