Reliability improvement of 980-nm laser diodes with a new facet passivation process

A facet passivation process especially for the realization of highly reliable 980-nm laser diodes (LDs) has been developed. This process includes three procedure steps which involve, in sequence: 1) ion irradiation; 2) interlayer deposition; and 3) ion-assisted deposition of coating material. We have named this passivation process "I-3." We applied this I-3 passivation process to our planar type 980-nm LDs, which were cleaved in air, and compared the aging characteristics between conventionally coated devices and I-3 passivated ones. As a result of a preliminary reliability test, I-3 passivated devices with 200-250 mW output showed stable operation over 3000 h at 50 °C. Moreover, a large scale reliability test is ongoing with 150-250 mW output powers and the results have shown no sudden failure during aging. This has meant a significant improvement of aging characteristics compared to conventional coating. In addition, we tried X-ray photo-electron spectroscopy (XPS) measurements to understand the physical phenomena associated with the I-3 process. A sample of air-exposed GaAs(110) substrate, corresponding to the facet, was found to have no GaOx and AsOx after I-3 processing at the interface. We attribute the improved aging characteristics to the excellent properties of the I-3 passivated facet despite the fact that it is cleaved in air. The I-3 process reduces nonradiative recombination that occurs due to excess and extrinsic surface states located at the facet caused by air exposure and resultant oxidation.