The strain-induced effects on the reduction of the threshold current density (J(th)) of AlGaInP visible lasers were investigated. For this paper, we fabricated strained multiple-quantum-well (SMQW) and unstrained multiple-quantum-well (MQW) AlGaInP broad contact lasers using a low-pressure organometallic vapor phase epitaxy (OMVPE). To perform a fair evaluation of the strain-induced effects, we newly introduced AlGaInP compressively strained quantum wells into the active region of the SMQW laser, and thus made the energy band structure of the SMQW laser almost the same as that of the MQW one. Comparing the J(th) of both lasers at the same lasing wavelength, we clarified that, for all the cavity lengths between 300 and 700 mum, more than a 4% decrease in J(th) was obtained by incorporating the SMQW structures, and the maximum reduction rate of 6% was achieved at 500 mum. We believe that this is the first report on the fair evaluation of the strain-induced effects in AlGaInP lasers. In addition, we clarified that, in the SMQW laser, the considerable decrease in the transparency current density J0 has contributed effectively toward J(th) reduction.
