Transfer-Printing of Tunable Porous Silicon Microcavities with Embedded Emitters

Here we demonstrate, via a modified transfer-printing technique, that electrochemically fabricated porous silicon (PSi) distributed Bragg reflectors (DBRs) can serve as the basis of high-quality hybrid microcavities compatible with most forms of photoemitters. Vertical microcavities consisting of an emitter layer sandwiched between 11- and 15-period PSi DBRs were constructed. The emitter layer included a polymer doped with PbS quantum dots, as well as a heterogeneous GaAs thin film. In this structure, the PbS emission was significantly redistributed to a 2.1 nm full-width at half-maximum around 1198 nm, while the PSi/GaAs hybrid microcavity emitted at 902 nm with a sub-nanometer full-width at half-maximum and quality-factor of 1058. Modification of PSi DBRs to include a PSi cavity coupling layer enabled tuning of the total cavity optical thickness. Infiltration of the PSi with Al₂O₃ by atomic layer deposition globally red-shifted the emission peak of PbS quantum dots up to ∼18 nm (∼0.9 nm per cycle), while introducing a cavity coupling layer with a gradient optical thickness spatially modulated the cavity resonance of the PSi/GaAs hybrid such that there was an ∼30 nm spectral variation in the emission of separate GaAs modules printed ∼3 mm apart.