High-index GaAs as a template for lithography-free nanostructures: mechanisms, orientations, and photonic integration pathways

Abstract High-index (H-I) GaAs surfaces enable lithography-free self-assembly of ordered nanostructures by exploiting step anisotropy, surface reconstructions, and directional adatom kinetics. We emphasize representative orientations—(311)A, (553)B, (775)B, and (631)A—where intrinsic anisotropy promotes periodic faceting and nanoscale corrugation. This review synthesizes the mechanisms behind periodic faceting and nanoscale corrugation—elastic relaxation, Marchenko-type period selection, and kinetic instabilities—and compiles qualitative trends reported for how orientation, temperature, and V/III ratio influence morphology, highlighting key open questions. We summarize device-relevant phenomena demonstrated to date—most notably polarization-engineered emission and vertical-cavity surface emitting lasers (VCSELs) on H-I GaAs—and discuss opportunities where the native anisotropy can facilitate distributed-feedback and Bragg elements, as well as metasurface-like functionalities, with minimal patterning. We also compare integration pathways toward silicon photonics (monolithic heteroepitaxy, thin-film bonding, micro-transfer printing), outlining benefits and limitations set by defects, uniformity, and reliability. We close with an outlook on real-time growth control and data-driven optimization, coupling in situ diagnostics with predictive faceting models to design morphology on demand. By unifying mechanisms, processing considerations, and integration pathways, this review positions H-I GaAs surfaces as a practical, scalable route to bottom–up photonic and quantum architectures.