Fabrication of GaAs/AlOx micropillars for small mode volume
Richard P. Mirin
Micropillar devices have shown promise as single photon sources for applications in quantum key distribution as well as single photon metrology and fundamental science. For higher temperature operation (77K), a high quality (Q) factor cavity and a small modal volume are necessary for enhanced spontaneous emission. Although high Q-factors have been demonstrated, achieving small modal volumes is difficult due to the limited index contrast available from lattice-matched Bragg layers. We overcome this limitation in a GaAs/AlAs material system by wet thermal oxidation of AlAs to form Al-oxide, creating very high index contrast Bragg layers. As a result, fewer Bragg layers are required for a given Q-factor, which should enable smaller mode volumes. We describe a fabrication process for such devices, utilizing a BCl3:Cl2:Ar etch, and demonstrate photoluminescence measurements of micropillars with 3 top and 5 bottom layers. They are measured to have Q-factors between 200-400 for approximately 1υm-3 υm diameters, respectively. These results indicate that high Q-factor devices may be possible while simultaneously reducing modal volume.
Fabrication of GaAs/AlOx micropillars for small mode volume, Journal of Vacuum Science and Technology B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=903375
(Accessed June 3, 2023)