Invited paper at APS March Meeting, March 2000
Minneapolis, MN


  Red, green and blue light emitters 
based on II-VI materials

                    Maria C. Tamargo (Department of Chemistry) 
                City College of CUNY, New York, NY 10031)


                    Red, green and blue (R-G-B) lasers and light emitting diodes are of interest for applications in 
                    high brightness, high definition displays. In these, the ability to integrate the three colors onto 
                    a single substrate is highly desirable for easier fabrication and miniaturization of the devices.
                    Furthermore, semiconductor based white-light emitters could also be used as light sources in 
                    many applications. Much effort is currently being devoted to the development of these devices, 
                    for which group-III nitrides and wide bandgap II-VI's have been the materials primarily explored.

                    During the past five years we have developed a family of II-VI wide bandgap materials that
                    exhibit promising characteristics. ZnMgCdSe quantum well (QW) structures grown
                    lattice-matched to InP substrates can emit light in the range of 2.1 to 3.0 eV, overlapping 
                    almost entirely with the visible spectrum range. For emission in the red, a strained QW with 
                    excess Cd can be used. Photopumped lasers in the R-G-B have been demonstrated from these
                    structures, where only the QW thickness or composition was varied. The growth conditions 
                    by MBE have been optimized so that defect densities are in the range of 10^4/cm^2. n-type
                    doping in the 10^18/cm^3 range is possible for the quaternaries. p-type conductivity can also 
                    be achieved, although the levels are still somewhat low (~10^16/cm^3). A lattice-matched
                    ZnSeTe layer (p~2 x 10^19/cm^3) has been developed for p+ ohmic contact formation.
                    Full-color LEDs have been fabricated and tested, and injection lasers are under development. 
                    To explore R-G-B integration, we have used selective area epitaxy and have grown adjacent
                    patterned QWs on a single substrate, which emit in the R-G-B regions. New directions include 
                    the design of a white-light LED that combines these three emitters in one.


Fig.1: Enjoying the banquet at the NAMBE Conference in Banff.

Fig.2: Conference organizers and friends at the NAMBE Conference Banquet, Banff.