Single-Material Bragg Reflectors and Their Applications in VCSELs

Abstract

We present single-material distributed Bragg reflectors (DBRs) fabricated by oblique-angle deposition of amorphous silicon (a-Si). The high and low refractive indices of a-Si films were obtained at two incident vapour flux angles (theta(alpha)) of 0 degrees and 80 degrees by determining the quarter-wavelength thicknesses of 67 nm at 0 degrees and 128 nm at 80 degrees. The fabricated single-material Bragg reflectors with only five pairs provide high reflectivity values of over 95%. The proposed DBRs were applied to intra-cavity contacted vertical-cavity surface-emitting lasers (VCSELs) to reduce fabrication costs and step. For the fabricated five pair a-Si/a-Si DBRs on VCSELs, the normalized stop bandwidth of 31.63% was measured while high reflectivity values over 95% were maintained over a wide wavelength range of 710 - 1020 nm. The fabricated VCSELs with D-a = 7 mu m obtained output power and threshold current, which are reasonable measured results.