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Tamm plasmons in metal/nanoporous GaN distributed Bragg reflector cavities for active and passive optoelectronics

We investigate Tamm plasmon (TP) modes in a metal/semiconductor distributed Bragg reflector (DBR) interface. A thin Ag (silver) layer with an optimized thickness (~ 55 nm from simulation) was deposited on nanoporous GaN DBRs fabricated using electrochemical etching on freestanding semipolar GaN substrates. The reflectivity spectra of the DBRs are compared before and after the Ag deposition and with that of a blanket Ag layer deposited on GaN. The results indicate presence of a TP mode at ~ 455 nm on the structure after the Ag deposition. An active medium can also be accommodated within the mode for optoelectronics and photonics. Moreover, the simulation results predict a sensitivity of the TP mode wavelength to the ambient (~ 4 nm shift when changing the ambient within the pores from air with n = 1 to isopropanol n = 1.3) , suggesting an application of the nanoporous GaN based TP structure for optical sensing.