New mechanisms of cavity facet degradation for GaN-based laser diodes

Abstract

We investigated the cavity facet degradation of unsealed GaN-based laser diodes (LDs). It was found that the decrease of optical output power accompanied by undulation for unsealed LDs is related to the facet degradation. Deposits containing Ga, Al, Si, and O were observed on the LD facet for the first time, explaining the reason for the degradation behavior. Considering the shorter wavelength of GaN-based laser diodes, we propose that the splitting of water molecules induced by high-energy photons triggers the oxidation of the facets and the deposition of SiO2. The shape of the deposits is closely correlated with the field distribution on the facet, influencing the LDs’ output power. Improving the tightness of the package is necessary to avoid the fast degradation of GaN-based LDs.