Two-Dimensional\nPhotonic Crystal Cavities in ZnSe\nQuantum Well Structures

ZnSe and related materials like ZnMgSe and ZnCdSe are\npromising\nII–VI host materials for optically mediated quantum information\ntechnology such as single photon sources (SPS) or spin qubits. Integrating\nthese heterostructures into photonic crystal (PC) cavities enables\nfurther improvements, for example, realizing Purcell-enhanced SPS\nwith increased quantum efficiency. Here, we report on the implementation\nof two-dimensional (2D) PC cavities in strained ZnSe quantum wells\non top of a novel AlAs supporting layer. This approach overcomes typical\nobstacles associated with PC membrane fabrication in strained materials,\nsuch as cracks and strain relaxation in the corresponding devices.\nWe demonstrate the attainment of the required mechanical stability\nin our PC devices, complete strain retainment, and effective vertical\noptical confinement. The structural analysis of our PC cavities reveals\nexcellent etching anisotropy. Additionally, elemental mapping in a\nscanning transmission electron microscope confirms the transformation\nof AlAs into AlO<sub><i>x</i></sub> by postgrowth wet oxidation\nand reveals partial oxidation of ZnMgSe at the etched sidewalls in\nthe PC. This knowledge is utilized to tailor finite domain time difference\nsimulations and to extract the ZnMgSe dispersion relation with small\noxygen content. Optical characterization of the PC cavities with cross-polarized\nresonance scattering verifies the presence of the cavity modes. The\nexcellent agreement between simulation and measured cavity mode energies\ndemonstrates the wide tunability of the PC cavity and proves the pertinence\nof our model. This implementation of 2D PC cavities in the ZnSe material\nsystem establishes a solid foundation for the future development of\nZnSe quantum devices.