Transferrable dielectric DBR membranes for versatile GaN-based polariton and VCSEL technology

We present an innovative process to realize planar GaN microcavities, based on transferrable high-quality oxidebased Distributed-Bragg-Reflector (t-DBR) membranes. Unlike the widely used direct DBR deposition, which is not always feasible, the concept of t-DBR membranes allows their versatile use as top mirrors in all kinds of vertical-cavity surface emitting geometry devices, including light emitting diodes and lasers. The process illustrated here starts by evaporating first a 4-pair SiO2/Ta2O5 DBR centered around 400 nm on a lithographically patterned GaAs substrate. The GaAs substrate is subsequently removed by wet-etching, and the released DBR membranes are transferred onto other templates for their use as top mirrors in microcavities. By transferring a 4-pair top DBR on an 8-pair bottom SiO2/Ta2O5 DBR, a distinct cavity mode appears due to the formed lambda/2 oxide cavity with a Q-factor of 110. If the 4-pair top DBR is transferred on 200 nm-thick GaN/AlGaN quantum well-containing membranes sitting on 10-pair bottom DBR5, complete all-dielectric nitride polariton structures are fabricated with pronounced strong-coupling characteristics.