Study on yellow/green semiconductor laser diodes

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We investigated Be composition dependencies of the luminescence property of BeZnSeTe II-VI compound semiconductors grown on InP substrates, resulting in obtaining bright luminescence in green region. Then we proposed a MgSe/BeZnSeTe superlattice(SL) barrier layer to confine carriers and optical field into the BeZnSeTe active layer, and improved the growth conditions such as the Zn irradiation at the SL interfaces. Based on these results, we fabricated light emitting devices. The device consisted of a BeZnSeTe quantum well active layer sandwiched by MgSe/BeZnSeTe SL barrier layers, MgSe/ZnCdSe SL n-cladding, and MgSe/BeZnTe SL p-cladding layers. In order to reduce the hetero barrier at the type-II hetero junction of the n-cladding and the n-barrier layers, we introduced a MgSe/ZnCdSe graded SL structure into the hetero junction. In the graded SL, the MgSe layer thickness ratio was gradually increased from 40 to 60 % along the growth direction from the n-cladding to the n-barrier side. By current injections, we observed green emissions around 530 nm. By aging tests of the devices under direct current injections, we obtained long life operations beyond 4800 h with no catastrophic degradation.In addition, we developed new p-cladding layer materials. We proposed a new doping technology that is inserting high p-doped ZnTe or ZnSeTe layers at regular intervals into ZnCdSe and MgSe/ZnCdSe SL layers which are inferior in p-doping, and experimentally proved the technology to be effective for p-doping. For example, the p-doping concentration of ZnCdSe which had been about 31016 cm-3 before was remarkably improved to be 8×1017 cm-3 using the technology. In the case of the MgSe/ZnCdSe SL, a high p-doping concentration of 4.6×1017 cm-3 was obtained at a wide bandgap of 2.33 eV. Applying the doping technology for the p-cladding layer, we fabricated light emitting devices. Consequently we obtained orange emissions around 600 nm.