Laser-assisted metalorganic chemical vapor deposition of zinc selenide epitaxial films

Laser-assisted metalorganic chemical vapor deposition has been used to grow epitaxial zinc selenide at temperatures as low as 200 °C. The metalorganic sources, dimethylzinc (DMZ) and diethylselenide (DESe), were photodissociated with radiation from a 193 nm ArF excimer laser passing parallel to a (100) GaAs substrate. A two-stage purge scheme prevented deposition on the windows while minimizing disturbances of the gas flow in the growth region. The temperature dependence for both thermal and laser-assisted film growth rates was examined. The reactor pressure was maintained at 100 Torr with a 10:1 DESe to DMZ ratio and 0.12 Torr partial pressure of DMZ. The laser was operated at a repetition rate of 20 Hz with pulse energies of 50 mJ. The laser-assisted growth rate of ZnSe remained approximately constant at 1 μm/h over the temperature range 200–400 °C. At higher temperatures the thermally driven process begins to become important. Photoluminescence analysis indicates that the material grown at 400 °C by the laser-assisted process is of better quality than films grown by either method at other temperatures.