砷銻氮化鎵/砷化鎵塊材光激發螢光特性研究

Photoluminescence study of GaAsSbN bulk epilayers on GaAs substrates

陳宗億(Tsung-Yi Chen)

指導教授 ： 林浩雄

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.02786

摘要

本篇論文的研究主題為氮銻砷化鎵塊材的光激發螢光(PL)特性。所有樣品皆以氣態源分子束磊晶法成長在砷化鎵基板上，經過800℃五分鐘快速熱退火後再加以分析。在變溫PL實驗量測中，每片樣品於低溫時皆可以觀察到主要尖峰有“S-shape”的行為，這是由帶尾能態(band-tail states)的發光所引起。進入高溫後主要尖峰的能量能夠符合Varshni公式，可證明其為帶對帶(band-to-band)發光。我們觀察到490℃成長的樣品比420℃及450℃成長的樣品有較明顯的“S-shape”行為，顯示較高溫成長樣品的成分均勻性較差。將樣品的室溫PL能隙與文獻中GaAsSb的能隙比較，我們發現加入氮後引起的能隙縮減量與銻成份多寡無關，其意味著在樣品中導電帶與價電帶的能帶位置可分別由氮及銻成份獨立調變。我們也發現所有樣品經由Varshni公式所擬合出的參數與氮成分相似的GaAsN相近。在PL譜中除了主要的尖峰外，我們在0.7eV附近也觀察到另一半寬達200meV左右的深能階發光尖峰。另外我們對PL的強度做了Arrhenius分析圖，在帶尾發光的部份，擬合出的活化能與其解離的溫度吻合，而在高溫帶間發光的部份，我們利用組態座標模型(configuration-coordinate model)成功地解釋高溫時擬合的活化能結果。在能與GaAs基板晶格匹配的樣品中，GaAs0.857Sb0.110N0.033室溫能隙低達0.84eV。顯示GaAsSbN為一極具潛力可應用於GaAs基長波長元件及串疊太陽能電池的材料。

關鍵字

砷銻氮化鎵 ； 光激發螢光 ； 變溫PL ； 瓦希尼 ； 活化能

並列摘要

The photoluminescence (PL) properties of dilute nitride GaAsSbN bulk epilayers are investigated. The GaAsSbN samples were grown on GaAs substrates by gas-source molecular beam epitaxy and characterized after a thermal annealing at 800℃ for 5 min. The main PL peak energy of all the samples shows “S-shape” behavior in the low temperature region, which is attributed to the behavior of the emission from band-tail states, and fits the empirical Varshni curve in the high temperature region, which evidences the band edge luminescence, in the temperature-dependent measurement. Samples grown at 490℃ are with more significant “S-shape” behavior than the ones grown at low temperature, indicating the worse compositional homogeneity in the former samples. Through a comparison between the room temperature PL energy and the GaAsSb energy gap reported in literatures, we found that the energy reduction due to nitrogen incorporation in GaAsSbN is independent of the Sb composition, implying that the energy positions of the conduction and valence band can be independently controlled by N and Sb composition respectively. We also found that the Varshni parameters of all the samples are close to those of GaAsN with similar N composition. Beside the main peak, a broad deep PL emission peaking at ~0.7eV was also observed in most of the samples. The Arrhenius activation energies of the PL intensity were investigated. The activation energy of the band-tail emission fits their dissociation temperature quite well. For band edge luminescence at high temperature, we use a configuration-coordinate model, which is considered to be related to the deep level emission, to explain its activation energy successfully. Among the epilayers grown coherently on the GaAs substrate, the lowest room temperature PL energy is 0.84 eV. This result suggests that GaAsSbN is a promising material for GaAs-based long wavelength optoelectronic devices and tandem solar cells.

並列關鍵字

GaAsSbN ； Photoluminescence ； temperature-dependent PL ； Varshini ； activation energy

參考文獻

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