Architecture-driven optical redshift and photoconductive response in In/Ga nitride digital heterostructures

Accessing low-energy optical transitions in c-axis III-nitrides remains challenging because high indium incorporation is constrained by lattice mismatch, thermal instability, strain, and compositional inhomogeneity. Here, we investigate shutter-defined In/Ga nitride digital architectures (DAs) grown by plasma-assisted molecular beam epitaxy as an alternative route for modifying the optical response without relying solely on conventional random-alloy composition control. High-resolution x-ray diffraction (XRD) reveals architecture-dependent structural modulation within a predominantly GaN-like framework, with no secondary crystalline phases detectable by XRD. The optical response varies strongly with the digital architecture; the shortest-period structure exhibits a reflectance-derived effective optical transition energy of approximately 2.24 eV, substantially below that of the GaN reference. Pronounced Fabry–Pérot oscillations further indicate sufficiently uniform optical thickness to sustain multiple-beam interference. Under 405 nm illumination, the same architecture exhibits a reproducible light-induced reduction in resistance and a seconds-scale post-illumination recovery. These results demonstrate that shutter-defined In/Ga nitride DAs provide a promising route for engineering low-energy optical transitions and the photoconductive response within the c-axis III-nitride platform.