Homoepitaxial growth of II-VI diode lasers produces blue-green laser emission
Developers at Eagle-Picher Laboratory (Miami, OK) and North Carolina State University (Raleigh, NC) achieved an important milestone recently when they observed laser emission from zinc selenide (ZnSe) based diode lasers grown on conducting ZnSe substrates. Previously, all reported II-VI diode lasers have been fabricated on gallium arsenide substrate, and efforts at extending device lifetimes have been thwarted by dislocations and defects caused by lattice mismatch between GaAs and ZnSe. Recent crystal-growth work at Eagle-Picher using aluminum-based dopants resulted in n-type conducting ZnSe crystals with dopant concentrations of 7 ¥ 1017 carriers/cm3 using its seeded physical vapor transport process.
The diode-laser structure, grown by molecular-beam epitaxy at North Carolina State University, consists of a p-on-n separate confinement heterostructure consisting of ZnMgSSe cladding layers, ZnSe light-guiding layers, and a single 60-200-Å strained ZnCdSe quantum well. Laser emission was recorded CW at 77 K and pulsed at higher temperatures at wavelengths between 507 and 517 nm. Now that they have created high-conductivity substrates, the next ste¥is to reduce the defects in the bulk ZnSe to permit long-lived laser operation.
