物理氣相傳輸法成長之硒化鋅單晶的製備及特性研究

Abstract

本論文裡主要是利用物理氣相傳輸法成長硒化鋅單晶晶體，並對其特性 逐一作分析，而本實驗所要強調的是所使用的長晶爐的特色不同於一般的 爐子。所採取的是單區域(single zone) 構造和一般選用的多區域(multi zone)有很大的差別溫度分佈便成為很大的考量，同時又不使用晶種( seed)來成長，成長方向與速度會受到很大的影響，所以困難度增加許多 ；除此本爐子也沒加裝空氣筒(reservoir) ，而此裝置主要的目的是利用 空氣統內的分壓來控制成長物質的化學計量比(stoichiometry) ，在缺乏 以上三個有利因素下更增加本實驗的困難度。 經由本實驗長出的晶體顏色偏向黃橘色，經過熱處理後顏色會比原晶體稍 暗些，此外我們也分別用蝕刻溶液處理晶體來觀察其蝕刻密度的分佈情形 ，並利用霍爾效應(Hall effect) 測其電性知道經過熱處理的晶體、其載 子濃度及遷移率(mobility)會提高而電阻值卻會明顯的降低，同時會隨熱 處理的時間增長導致明顯的變化；除此我們利用低溫激發光譜來鑑定其缺 陷結構，以及紅外光譜及可見光譜比較熱處理前後的穿透度，最後我們更 利用電子微探針分析(EPMA)鑑定主成份，所得的結果都顯示了熱處理過程 的重要性。 In this study, the zinc selenide was grown by using the dissoci- ative sublimation method. There are three major features existed in our furnace which are different from the general physical vapor tr- ansport one. First, we adopt the single zone to grow the crystals instead of the multi zone. It is consequently hard to control the temperature profile and grow high quality crystals. Secondly, we can't obtain the seed crystal which can reduce growth time and avoidto nucleate at the wall of ampoule to proceed our trial. Third, we don't have the reservoir part in our furnace. To adjust the tempera- ture of reservoir is efficient to control the composition of vapor in the capsule. The color of grown crystals reveals yellow-orange. After heat tr-eatment,the color of Zn-dip crystals is darker than that of as-growncrystals. The density distribution of etch pit of the crystals is revealed by employing etching solution. In addition, the relation among the carrier concentration, resistivity and mobility is establ-ished. The carrier concentration and mobility increase with increas-ing annealing time,but resistivity vice versa.We further demonstratethe defect structure of ZnSe crystals by using the low temperature photoluminescence measurement. The donor-acceptor pair(DAP) is obvi-ously demonstrated in the measured results. In the mean time we mea-sure the transparency by employing the IR and UV- visible. We found the heat treatment process plays a key role in the properties of thegrown crystals on the basis of the experimental results.