- 學位論文
生長於氮化鎵模板上氮化鋁鎵的應變行為與其對鋁成份漸變氮化鋁鎵內極化感應產生的p-型性能之影響
Strain Behaviors of AlGaN Grown on GaN Templates and Their Effects on the Polarization-induced p-type Performance of Al-gradient AlGaN
摘要
我們首先在氮化鎵模板上生長一系列厚度170nm均勻鋁濃度氮化鋁鎵樣品，透過倒晶格空間的量測我們得知當鋁濃度大於45%時其所受伸張應力開始釋放。為了瞭解氮化鎵模板上氮化鋁鎵的應變行為與其對鋁成份漸變氮化鋁鎵內極化感應產生的p-型性能之影響，我們在氮化鎵模板上生長鋁成份漸變氮化鋁鎵之前先生長一層均勻高鋁濃度氮化鋁鎵夾層，我們改變這夾層之厚度來比較其結果。由實驗結果得知，越厚的氮化鋁鎵夾層會減弱鋁成分漸變氮化鋁鎵層內所受的伸張應力並減少其極化場的梯度，進而導致其電洞濃度降低，此外我們也比較相同鋁濃度漸變梯度但不同鋁濃度漸變範圍之樣品，我們發現平均鋁濃度越高，其伸張應力釋放越多，導致其電洞濃度會越高。這種應力釋放的效應能有效的抑制電洞濃度隨著鋁濃度上升而下降的趨勢，平均鋁濃度大於45%時，電洞濃度呈現增加的趨勢，當樣品內有均勻鋁濃度氮化鋁鎵夾層時，這種抑制效果會變弱。
並列摘要
The strain relaxation behaviors of AlGaN layers of fixed Al contents on GaN template through the measurements of reciprocal space mapping are first studied. The tensile strain in an Al-fixed AlGaN of ~170 nm in thickness on GaN starts to relax when Al content is higher than 45 %. Then, for understanding the effect of tensile strain relaxation on the p-type behavior of an Al-gradient AlGaN layer, we prepare a few series of Al-gradient AlGaN sample on GaN template with varied thickness of a fixed-Al AlGaN interlayer and compare their results. A larger interlayer thickness results in a weaker tensile strain and hence a smaller polarization gradient in the Al-gradient AlGaN layer such that hole concentration is reduced. Also, in the comparisons between the Al-gradient samples with different average Al contents, a sample of a higher Al content leads to a stronger tensile strain relaxation and hence a higher hole concentration. This strain relaxation effect counteracts the intrinsic trend of hole concentration decrease with increasing Al content to show the increasing hole concentration trend when the average Al content is higher than 45 %. This counteraction effect becomes weaker when a fixed-Al AlGaN interlayer is added to a sample.
參考文獻
延伸閱讀
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