Effects of total gas velocity during growth of undoped GaN epitaxial layer on sapphire (0001) substrate by horizontal MOCVD
Effects of total gas velocity during growth of undoped GaN epitaxial layer on sapphire (0001) substrate by horizontal MOCVD
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DOI：
10.1016/j.jcrysgro.2004.03.003
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发表时间：
2004-06-01
影响因子：
1.8
通讯作者：
Cho, SI
中科院分区：
文献类型：
--
作者：
Kwon, MS;Cho, SI
研究了在（0 0 0 1）蓝宝石衬底上，在30 0 7 Torr的低压下，采用两步生长法在水平MOCVD反应器中生长非掺杂GaN外延层时总气速的影响。在GaN生长过程中，我们改变了进入主运行线的H-2推动气体的流量，以改变衬底上的总气体速度。气体总流速的变化对未掺杂GaN外延层的光致发光光谱有很大的影响。在我们研究的两步条件下，在总气速为0.21-0.46 m/s的范围内，所有样品都没有显示出黄色发光带，这不受生长温度从1080 ℃到1020 ℃降低30 ℃的影响。相反，我们的样品显示了在我们的推动气体的流量范围内的极端条件下的施主-受主对（DAP）复合跃迁，即总气体速度。在较低的气体流速范围内，I-2的带边发射随气体流速的增加而发生蓝移。DAP跃迁的存在和带边发射的峰值位置将是获得工艺窗口和优化未掺杂GaN外延层生长期间的工艺变量的有用指示。(C)2004 Elsevier B. V.保留所有权利。
We have studied the effects of total gas velocity during the growth of undoped GaN epilayers on (0 0 0 1) sapphire substrate at a low pressure of 3007 Torr via a two-step growth condition in a horizontal MOCVD reactor. We changed the flow rates of H-2 push gas into the main run line to change total gas velocity on the substrate during the GaN growth. The photoluminescence spectra of undoped GaN epilayers were strongly affected by the changes of the total gas velocity. In a total gas velocity range of 0.21-0.46 m/s under the two-step condition in our study, all samples showed the absence of yellow luminescence band, which was not affected by the changes of the growth temperature from 1080degreesC to 1020degreesC by a 30degreesC decrease. Instead, our samples showed the donor-acceptor pair (DAP) recombination transitions at the extreme conditions in our range of the flow rates of push gas, i.e. total gas velocity. The band-edge emission of I-2, showed a blue-shift with increasing the total gas velocity in a lower velocity regime in this study. The presence of DAP transitions and the peak position of band-edge emission would be a useful indication to obtain a process window, and to optimize the process variables during the growth of an undoped GaN epilayer. (C) 2004 Elsevier B.V. All rights reserved.