利用連續流動型反應槽與圖案化ZnAl2O4緩衝層進行點陣列氧化鋅側向磊晶成長之研究

Lateral Epitaxial Overgrowth of ZnO Layers on Patterned ZnAl2O4 Buffer Layers by Continuous Flow Reactor

林宣辰

氧化鋅 ； 側向磊晶成長 ； 水熱法 ； 晶體缺陷 ； 圖案化製程 ； ZnO ； lateral epitaxial overgrowth ； hydrothermal growth ； crystal defects ； patterning process

義守大學材料科學與工程學系學位論文

2016年

碩士

陳厚光

繁體中文

由於成長高品質氧化鋅磊晶膜層對於氧化鋅於光電元件的製作將會是相當關鍵。為了可以進一步降低磊晶膜層中差排密度，可以進一步搭配圖案化製程，進行側向磊晶成長(Lateral epitaxial overgrowth, LEO)。在前期研究中已證實可透過 “線陣列”圖案化緩衝層陣列輔助，並搭配低溫水熱法製程在藍寶石基板上進行氧化鋅無遮罩式側向磊晶成長，並獲得低差排密度癒合氧化鋅膜層。然而磊晶膜層中仍存在著Wing tilt效應(約0.1o)；為了改善Wing tilt效應，本研究將提出另一種圖案設計的緩衝層─六角形點陣列，來進行側向磊晶成長。此外，一般的壓力釜進行長時間水熱法成長，其水溶液前驅物濃度將無法長時間維持穩定晶體成長，因此不可避免需中斷成長並更換新鮮前驅物溶液，因此進而導致增加汙染風險。在本研究中將開發“連續流動型反應槽”，以蠕動幫浦進行前驅物溶液的補充，使反應槽內前驅物維持在一定的濃度; 試片可進行連續長時間水熱法成長。實驗結果顯示膜厚的成長速率約為0.4 μm/hr，並且可以穩定的進行24 hr以上的連續晶體成長。將進一步以連續流動型反應槽，在六角形點陣列圖案化緩衝層上進行連續長時間ZnO側向磊晶成長。經過84小時以上成長，可以獲得完全連續癒合的膜層。從X光繞射搖擺曲線分析結果證實在點陣列上進行LEO成長之氧化鋅膜層幾乎完全沒有Wing tilt效應。膜層平均差排密度為3×108 cm-2。在癒合LEO膜層不同部位之顯微結構，分別透過穿透式電子顯微鏡及微區光激發螢光量測來進行探討。

The growth of high quality zinc oxide (ZnO) epitaxial layers is very critical for the fabrication of ZnO-based optoelectronic device. To further reduce dislocation density in epi-layer, lateral epitaxial overgrowth (LEO) integrating with patterning processing had been proposed. In previous works, maskless LEO of ZnO with low dislocation density on sapphire substrates in low temperature aqueous solution, through the assistance of stripe-patterned buffer layer, was reported. However, a slight wing tilt (a tilted angle of 0.1o) remained in the coalesced LEO ZnO layer grown on a stripe-patterned buffer layer. In order to minimize the degree of wing tilt, in this work, maskless LEO of ZnO layer was performed on the patterned buffer layer using the circular window with hexagonal array. In addition, while using conventional autoclave vessel to implement long-duration hydrothermal growth, the soluble Zn species in the growth solution is insufficient to maintain a stable growth rate. Hence, the crystal growth is inevitably subject to interruption to refresh growth solution, resulting in increasing the risk of contamination. Hence, a continuous flow reactor, which can maintain the concentration of the zinc species in solution during the course of crystal growth by continuously delivering precursor solution, to suit the requirement of long-duration crystal growth, was developed. The growth rate of ZnO epitaxial layer grown by the continuous flow reactor was estimated to be about 0.4μm/hr. It was evident that the continuous flow reactor was competent to perform the long-duration epitaxial growth (>24 hr). Furthermore, the continuous flow reactor was employed to perform long-duration LEO of ZnO layers on hexagonally patterned buffer layer. After LEO growth for 84h, the fully coalesced, continuous, epitaxial layer can be obtained. Based on X-ray diffraction rocking curve (XRC) measurement, the wing tilt effect was almost absent in the coalesced LEO ZnO layer. The average dislocation density in the coalesced LEO layer was about 3×108 cm-2. The site-specific microstructural characterization of LEO-grown ZnO layer was implemented by transmission electron microscopy and micro photoluminescence measurement.

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1. 顏士喬(2017)。高分子複合材輔助水熱法成長雙軸向規則排列氧化鋅晶體薄膜。義守大學材料科學與工程學系學位論文。2017。1-121。