  ZnSe and related materials like ZnMgSe and ZnCdSe are promising II-VI host
materials for optically mediated quantum information technology such as single
photon sources or spin qubits. Integrating these heterostructures into photonic
crystal (PC) cavities enables further improvements, for example realizing
Purcell-enhanced single photon sources with increased quantum efficiency. Here
we report on the successful implementation of two-dimensional (2D) PC cavities
in strained ZnSe quantum wells (QW) on top of a novel AlAs supporting layer.
This approach overcomes typical obstacles associated with PC membrane
fabrication in strained materials, such as cracks and strain relaxation in the
corresponding devices. We demonstrate the attainment of the required mechanical
stability in our PC devices, complete strain retainment and effective vertical
optical confinement. Structural analysis of our PC cavities reveals excellent
etching anisotropy. Additionally, elemental mapping in a scanning transmission
electron microscope confirms the transformation of AlAs into AlOx by
post-growth wet oxidation and reveals partial oxidation of ZnMgSe at the etched
sidewalls in the PC. This knowledge is utilized to tailor FDTD simulations and
to extract the ZnMgSe dispersion relation with small oxygen content. Optical
characterization of the PC cavities with cross-polarized resonance scattering
spectroscopy verifies the presence of cavity modes. The excellent agreement
between simulation and measured cavity mode energies demonstrates wide
tunability of the PC cavity and proves the pertinence of our model. This
implementation of 2D PC cavities in the ZnSe material system establishes a
solid foundation for future developments of ZnSe quantum devices.
