Towards monolayer control of interfaces for short-wavelength infrared transitions in ScAlN/GaN asymmetric double quantum wells

Designing novel photonic materials relies on the ability to modulate semiconductor band structure with monolayer precision. We employ conduction band engineering and modifications of the molecular-beam epitaxy (MBE) process to tune the optical transitions of Sc0.14Al0.86N/GaN/Al(Sc)N/GaN double quantum well (DQW) structures above 800 meV. The incorporation of rare-earth scandium into traditional nitride semiconductors opens new design space by enabling low-defect nitride heterostructures lattice-matched to GaN. However, recent studies found that significant intermixing at interfaces considerably distorts the band profile of ultra-thin GaN/ScAlN quantum wells. To overcome these challenges, the structure–property relationships of Sc-containing DQWs were assessed by correlating infrared intersubband absorption with high-resolution x-ray diffraction and electron microscopy techniques. Computational simulations of quantum confinement and carrier distribution explain the observed experimental trends of intersubband absorption associated with variation of layer widths, middle barrier composition, and doping density. MBE growth in a metal-accumulation mode is found to be crucial for improving structural conformity to design by reducing interface roughness and thickness and for reaching the telecom-relevant spectral range.