Geometry-Preserving Lateral Epitaxial Overgrowth for Buried Dielectric Photonic Crystals

Abstract

Photonic crystal surface-emitting lasers (PCSELs) and topological cavity surface-emitting lasers (TCSELs) require precise, reproducible nanostructures embedded within III-V semiconductor matrices, yet conventional void-based fabrication is geometry-sensitive and difficult to control across mixed pattern shapes and sizes. We demonstrate a geometry-preserving buried dielectric approach using InP lateral epitaxial overgrowth (LEO) in which lithographically defined dielectric patterns are encapsulated with high dimensional fidelity regardless of pattern geometry. Selective InP nucleation, lateral overgrowth, and coalescence are established on triangular, polygonal, and stripe dielectric patterns with feature sizes ranging from 270 to 1100 nm. Threading dislocation density and stacking fault density are reduced by more than 50× and 4×, respectively, through selection of pattern sizes below 300 nm and avoidance of dielectric sidewalls oriented along ⟨110⟩ crystallographic directions. This InP LEO platform has already enabled optically pumped buried-dielectric PCSELs emitting at 1.5 μm, establishing a foundation for PCSEL and TCSEL devices requiring complex, multi-geometry photonic crystal designs.