新型蓝光衬底材料LiAlO_2晶体的生长和缺陷分析

Growth and Defects of Novel Substrate Material LiAlO 2 Crystal

ＬｉＡｌＯ２和ＧａＮ的晶格失配率只有１．４％，是一种很有希望的ＧａＮ外延生长衬底材料。本文利用温度梯度法生长出了透明的ＬｉＡｌＯ２单晶，并通过化学浸蚀、光学显微镜、透射电子显微镜、同步辐射Ｘ射线貌相术对晶体中的缺陷进行了检测。结果表明：ＬｉＡｌＯ２在钼坩埚中无籽晶自由凝固结晶时，是沿（１００）方向生长。用温度梯度法生长的ＬｉＡｌＯ２晶体质量良好，晶体中无气泡和包裹物。在ＬｉＡｌＯ２（１００）晶面上测得的位错密度为（３．８～６．０）×１０４ｃｍ－２，晶体中的主要缺陷为亚晶界或镶嵌结构，可能是由于温场不稳定、生长速率太快造成的。

The lattice mismatch between LiAlO 2 and GaN is only 1.4%, so LiAlO 2 is expected to be a promising substrate for the epitaxy of GaN. In present work, large sized and transparent LiAlO 2 single crystal has been grown by using temperature gradient technique. The crystal quality was characterized by the methods of chemical etching, optical microscope, TEM and synchrotron source X ray topography. The results showed that LiAlO 2 grew along 〈100〉 direction when it crystallized without using seed in Mo crucible. The crystal was free from bubbles and inclusions, and the dislocation density measured on (100) crystal plane was about (3.8￣6.0)×10 4 cm -2 . The main defects were subgrain boundaries, which may be caused by the fluctuation of temperature field in the furnace or over high growth rate. These two parameters should be optimized in further.