John A. Baumann

Reliability of wide bandgap semiconductor diode lasers

Research into new material systems to both extend the operating wavelength and improve the performance of the GaAs/AlGaAs material system has led to several insights into the reliability of wide bandgap (E(g) greater than 1eV) semiconductor lasers. Strained InGaAs lasers, operating in the wavelength range 0.9-1.1 micron, have eliminated sudden failures and exhibited very low gradual degradation rates. Strained InAlGaAs lasers, a possible replacement for AlGaAs lasers at 0.8 micron have shown the potential to both eliminate sudden failures and improve gradual degradation as compared to AlGaAs lasers. Finally, visible GaInP lasers, operating at 0.65 micron, have eliminated sudden failures and exhibited surprising gradual degradation characteristics for lasers operating at modest efficiencies. Specific results and subsequent conclusions with the supporting life test characteristics and failure analysis are contained in this work.

Evaluation of diode laser failure mechanisms and factors influencing reliability

A number of recent observations promise to have a significant impact on semiconductor laser reliability. Device life has been seen to depend on device architecture and processing, epitaxial structure and growth parameters, and alloy chemistry. Comparative studies have shown that dry-etched devices are at least as reliable as oxide-defined lasers, and that median life is a function of the quantum well count in the structure. Improved reliability has also been obtained by using longer cavity devices to improve thermal performance at the lasing junction. Elimination or reduction in the occurrence of sudden or freak failures which limit median life of diodes has been achieved by studying the factors influencing the growth and propagation of dark line defects (DLDs). Operating temperature, chip geometry, alloy effects, and epitaxial growth parameters have all been shown to affect device reliability.