Formation mechanism and separation of the mesoporous GaN Distributed Bragg reflectors from sapphire substrate

The mesoporous GaN (MP-GaN) Distributed Bragg reflectors (DBRs) with tunable spectral stop-band across visible spectrum are fabricated by electrochemical etching in the neutral solution. The formation mechanism of MP-GaN layer in the DBR is first studied via the differential interference contrast microscopy. Then the self-standing MP-GaN DBR is first separated from the sapphire substrate via an annealing technology, and is transferred to a foreign substrate. The transferred MP-GaN DBR with high quality presents high reflectivity (>90%) and large stop-band widths (>100 nm). And the improved crystalline quality is due to the reduced defect density and the total stress relaxation of the GaN film. The high reflectivity and good crystalline quality render the lift-off MP-GaN DBR a promising application prospect in flexible optoelectronic devices.