GAS EFFECT ON TRANSPORT RATES OF ZNSE IN CLOSED AMPOULES

Gas effects on the transport rates of ZnSe in closed systems were inve stigated. An ampoule (10 mm x 90 mm) was fabricated from a quartz tube which had been cleaned in a hydrogen flow at about 1000 degrees C for 5 hours. The source material was polycrystalline ZnSe of 6N purity wi th about a 3 to 6 mm particle size. Ar, H-2 or He gas was introduced u nder pressure p, along with the source. The ampoule was sealed and pla ced in an electric furnace for 15 hours. The source temperature was 10 69 degrees C, and the growth end temperature was 1048 degrees C. Here, the transport rate was defined as J. J(argon) started to decrease at p(argon) = 9 Torr, J(hydrogen) decreased at p(hydrogen) = 45 Torr, and J(helium) was almost constant in all over the p(helium) range. The th ermal conductivity of helium is almost 10 times that of argon gas, but similar to that of hydrogen gas. It was considered that J(hydrogen) w as intermediate between J(helium) and J(argon) since hydrogen is a rea ctive gas. It was concluded that J(argon) and J(hydrogen) had a diffus ion limited mass transport region.