熱退火對氮銻砷化鎵能隙及原子結構的影響

本論文我們研究利用氣態源分子束磊晶成長的氮銻砷化鎵樣品在熱退火前後的能隙和原子結構的改變。經由光激發螢光和光學吸收譜的量測，此材料的能隙在經過750C熱退火之後有著明顯的能隙藍移現象。這些氮銻砷化鎵樣品在經過熱退火後的能隙值與文獻利用能帶彎曲模型所計算的能隙很接近。此外，氮和銻可以獨立控制縮減此材料的能隙。在這樣的基礎下，我們提出雙能帶彎曲模型並用來說明氮和銻的加入可分別獨立控制砷化鎵的導電帶和價電帶能量。我們也研究了氮銻砷化鎵在經過熱退火後能隙藍移的原因。我們相信“氮原子對”存在於熱退火前的氮銻砷化鎵樣品，其能隙比雙能帶彎曲模型理論計算值還低。在經過熱退火處理之後，“氮原子對”逐漸分離成“獨立氮”的形式並導致能隙藍移。將調置光譜量測的訊號經由Karmers-Kronig 模組轉換後的分析，我們可以解析出各種“氮原子對”和“獨立氮”所造成訊號。當熱退火溫度上升時，這些訊號逐漸混合到“獨立氮”的訊號。為了更進一步找尋可以支持“氮原子對”分離理論的證據，我們利用國家同步輻射中心20A光束線量測了氮的K-edge X 光吸收近邊緣頻譜並研究氮銻砷化鎵短範圍結構的變化。我們使用價力場模型建立多個216原子的超晶格，分別包含了許多不同的結構，包括“獨立氮”、“氮原子對”、氮氫複合物等等。我們以氮為中心，建構一個381原子的球型原子堆並利用模擬軟體FEFF9來模擬氮的光吸收近邊緣頻譜。藉由比較實驗值和模擬值，我們認為“氮原子對”存在於熱退火前的氮銻砷化鎵樣品。當熱退火850C、5分鐘後“氮原子對”轉換成獨立氮氫複合物。

關鍵字

氮砷銻化鎵；熱退火；能隙藍移；分子束磊晶；氮原子對；能帶彎曲模型；同步輻射；氮氫複合物

並列摘要

In this dissertation, the effects of thermal annealing on the energy gap and atomic structure of GaAsSbN, grown by gas source molecular beam epitaxy, have been investigated. From the measurement of photoluminescence and optical absorption, significant blue-shifts in energy gap, resulting from annealing with a temperature higher than 750C, were observed. The energy gap of the annealed GaAsSbN follows the band anticrossing model (BAC) reported in literature. Furthermore, the energy gap reduction can be independently controlled by Sb and N compositions. On the ground of this finding, we proposed a double BAC model, in which we suggest that N and Sb compositions control the energy of conduction and valence band respectively. Besides, the origin of the blue shift induced by thermal annealing is investigated. We believe N pairs NN1 responsible for the low energy gap of the as-grown GaAsSbN. Thermal annealing dissociates the pair into isolated N atoms, resulting in the blue-shift in energy gap. From the Kramers-Kronig modulus of photoreflectance measurement, we resolve multi-peaks relevant to different N pairs and isolated N. When the annealing temperature increases, the peaks gradually merge to that of isolated N. To further support the proposed N pairs dissociation theory, we performed N K-edge X-ray absorption near-edge spectroscopy (XANES) using the beam line 20A of National Synchrotron Radiation Research Center to study the short range structure of GaAsSbN. We use valence force field model to generate supercells with 216 atoms containing different atomic structures, including isolated N, NN1 pair, N-HBC complex, and so on. FEFF9 code, purchased from University of Washington, was then used to simulate the XANES spectra of N-centered cluster of 381 atoms, developed from supercells with different atomic structures. By comparing the experimental results with the simulated XANES, we conclude that NN1 pair existed in the as grown GaAsSbN sample. After thermal annealing at 850 C for 5 min, NN pairs transform into isolated N-HBC complex.

並列關鍵字

GaAsSbN ； annealing ； blue shift ； MBE ； nitrogen pair ； band anticrossing ； synchrotron radiation ； N-HBC complex

參考文獻

S. Wicaksono, S. F. Yoon, K. H. Tan, and W. K. Cheah, “Concomitant incorporation of antimony and nitrogen in GaAsSbN lattice-matched to GaAs,” J. Cryst. Growth 274, 355 (2005).

J. C. Harmand, A. Caliman, E. V. K. Rao, L. Largeau, J. Ramos, R. Teissier, L. Travers, G. Ungaro, B. Theys, and I. F. L. Dias, “GaNAsSb: how does it compare with other dilute III–V-nitride alloys?,” Semicond. Sci. Tchnol. 17, 778 (2002).

G. Ungaro, G. Le Roux, R. Teissier, and J.C. Harmand, “GaAsSbN: a new low-bandgap material for GaAs substrates,” Electron. Lett., 35, 1246, 1999.

J. C. Harmand, G. Ungaro, L. Largeau, and G. Le Roux, “Comparison of nitrogen incorporation in molecular-beam epitaxy of GaAsN, GaInAsN, and GaAsSbN,” Appl. Phys. Lett. 77, 2482 (2000).

T.C. Ma, Y.T. Lin, T.Y. Chen, L.C. Chou, and H. H. Lin, “Incorporation behaviors of group V elements in GaAsSbN grown by gas source molecular beam epitaxy,” The 19th Indium Phosphide and Related Material, WeA1-5 (2007).

國際替代計量

熱退火對氮銻砷化鎵能隙及原子結構的影響

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