Degradation experiments for AlGaInN-based laser diodes were conducted for the purpose of constructing a possible model of the degradation mechanism. Lasers in this experiment were aged under 30 mW continuous-wave operation at 60 °C, and the lifetime was defined as the time at which the operating current increased by 20%. The lifetime was found to be dependent on the dislocation density of the basal ELOGaN layer, with the degradation rate being almost proportional to the square root of aging time. A model of degradation in which degradation is governed by a diffusion process is proposed based on these results. Although the model describes the experimental findings well, further investigation is considered necessary before the degradation mechanism in AlGaInN lasers can be fully understood.

AlGaInN‐based blue–violet laser diodes with a single broad‐area stripe emitter were successfully fabricated on GaN substrates. Three stripe widths were examined; 10, 50, and 100 μm, and the maximum light output power of 0.94 W under cw operation at 20 °C was achieved for the sample with a stripe width of 10 μm. A super high‐power laser diode array was fabricated using 11 of these high‐performance laser chips, with a resultant output power of 6.1 W under cw operation at 20 °C. This result represents the highest reported output power for blue–violet laser diodes. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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We successfully developed high‐power and long‐lived pure blue laser diodes (LDs) having an emission wavelength of 440–450 nm. The pure‐blue LDs were grown by metalorganic chemical vapor deposition (MOCVD) on GaN substrates. The dislocation density was successfully reduced to ∼106 cm–2 by optimizing the MOCVD growth conditions and the active layer structure. The vertical layer structure was designed to have an absorption loss of 4.9 cm–1 and an internal quantum efficiency of 91%. We also reduced the operating current density to 6 kA/cm2 under 750 mW continuous‐wave operation at 35 °C by optimizing the stripe width to 12 µm and the cavity length to 2000 µm. The half lifetimes in constant current mode are estimated to be longer than 10000 h. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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