Research undertaken by 3M in St. Paul, Minn., culminated in the demonstration of the world's first laser diodes fabricated from II-VI semiconductor materials. These devices emit coherent radiation at 490 nm in the blue-green portion of the spectrum. They are disclosed generally in the Qiu et al. U.S. patent application Ser. No. 07/700,580, filed May 15, 1991 now U.S. Pat. No. 5,213,998, and entitled Method For Making An Ohmic Contact For P-Type Group II-VI Compound Semiconductors, and the Haase et al. article Short Wavelength II-VI Laser Diodes, Conference Proceedings for Gallium Arsenide and Related Compounds, 1991 Institute of Physics Conference Series, No. 120, pp 9-16.
The light-generating (active) layers in the above-described laser diodes include strained Cd.sub.x Zn.sub.1-x Se single quantum wells grown by conventional molecular beam epitaxy (MBE) techniques. Unfortunately, the composition and thickness of the random CdZnSe alloy is difficult to control by this process. Luminescence efficiency is also relatively poor. These characteristics limit the overall efficiency of the devices.
It is evident that there is a continuing need for improved laser diodes. For wide spread commercial viability, the devices must be capable of efficiently generating high intensity beams of light at room temperatures. Fabrication techniques for laser diodes having these characteristics are also needed.
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