Abstract

ZnMgSSe-based II-VI semiconductors are promising materials for making blue and green laser diodes (LD). Haase et al. reported the first demonstration of ZnCdSe quantum well lasers[1]. Room temperature (RT) continuous-wave (CW) operation was the next milestone for practical usage of blue and green LDs. Recently we have achieved RT CW operation of ZnCdSe/ZnMgSSe lasers. To realize RT operation, lattice-matched heterostructures with sufficiently large electrical and optical confinement are essential. These conditions can be satisfied with employing a novel ZnMgSSe alloy, which was originally developed by Okuyama et al.[2], for cladding layers. This alloy offers a wide range of bandgap energy from 2.7 to ~4 eV, while maintaining lattice matching to a GaAs substrate, which gives us the flexibility in designing the LDs. We fabricated a separate confinement heterostructure (SCH), having ZnMgSSe cladding layers, ZnSe waveguiding layers, and a ZnCdSe multiple-quantum-well(MQW) active layer. The structure shown in fig.1 was grown on a (001) n-GaAs substrate by molecular beam epitaxy(MBE). Figure 2 shows the light output against current characteristics at RT measured under continuous and pulsed-current conditions. The CW threshold current (I_th) is 45 mA corresponding to a threshold current density of 1.5 kA/cm². The typical laser threshold voltage is 17 V. The lasing wavelength is 523.5 nm under continuous operation as shown in figure 3. We have also observed blue stimulated emission at 489.9 nm (figure 4). This blue laser has the same structure as the blue-green laser except for employing a less Cd containing active layer and a p-ZnTe/p-ZnSe MQW layer as a p-contact layer in order to reduce the operating voltage. This MQW layer leads to the operating voltage of 6.3 V.

© 1994 Optical Society of America