磷銻化鎵與砷磷銻化鎵之結構特性研究

在本論文中，我們分析了GaPSb與GaAsPSb兩種合金的結構特性，從倒置晶格空間圖譜以及拉曼散射頻譜中，發現這些晶體具有良好的長距結構有序(long-range order)，然而我們在拉曼散射頻譜中觀察到GaP-like LO模態出現一鍵雙模的現象，且具有非常不對稱以及極大半寬的線形；我們認為是由於鍵結扭曲，也就是短距結構失序(short-range disorder)，使各鍵偏離了最低能量的位置，從而加強了非和諧交互作用(anharmonic interaction)，使得晶格波被強烈地衰減造成了空間侷限。因此我們利用空間相關模型(spatial correlation model)來擬合這個具有極大不對稱的拉曼譜型。此外，我們也使用了同步輻射X光來測得這些材料的X光吸收頻譜，並且經由延伸X光吸收精細結構(extended X-ray absorption fine structure)的分析，可以發現內部的鍵長趨向所對應的二元原始鍵長，進而得知鍵彎曲為畸變能的主要來源。為了更進一步探討這些樣品的內部結構，我們也使用了價立場模型(valence force field model)模擬GaPSb與GaAsPSb的鍵結扭曲；發現次鄰接原子結構對於GaP聲子色散關係有著不同的影響。在GaPSb以Ga原子為中心的四面體單位晶胞中，若其四個次鄰接原子為2Sb2P時，此種單位晶胞的伸張能(stretching energy)最低，但彎曲能(bending energy)最大，造成在拉曼頻譜中較對稱GaP-like LO+線形的貢獻，其他單位晶胞則是形成具有較大半寬的GaP-like LO-。另一方面，在GaAsPSb中，Ga原子為中心與次鄰接1As1P2Sb原子形成的四面體單位晶胞有著最小的伸張能，但是形成此種晶胞的機率太低，所以對拉曼頻譜沒有造成貢獻，故在GaAsPSb的拉曼頻譜中，只有觀察到一個GaP-like LO模態。

關鍵字

磷銻化鎵；砷磷銻化鎵；鍵結扭曲；長距結構有序；短距結構失序；非和諧交互作用；空間相關模型；延伸X光吸收精細結構；價立場模型

並列摘要

In the thesis, we study the structural properties of GaPSb and GaAsPSb alloys. Results from reciprocal space mapping and Raman scattering spectra suggest that long-range order remains in these alloys. However, we also find a behavior of one bond → two modes along with broad line width and asymmetry. We believe that the atoms deviate from their minimum energy sites because of bond distortion or short-range disorder, leading to strong anharmonic effect, which cause the attenuation of phonon wave. Therefore, we use spatial correlation model to fit the broad and asymmetric line shape successfully. In addition, we also use synchrotron radiation X-ray to measure the X-ray absorption of these alloys. From the fitting results of extended X-ray fine structure, we know the bond length is prone to be its binary one; so the major ingredient of bond distortion is bond bending. In order to further study of bond distortion. We utilize valence force field model to calculate the distortion of the atoms on a supercell of 1000 atoms. We find that the nearest neighbor atoms affects the phonon dispersion relation. In a Ga-centered tetrahedral unit cell with 2P2Sb atoms of GaPSb supercell, the stretching energy of Ga-P bond is very small but bending energy is the strongest. We ascribe the GaP-like LO+ line shape with better symmetry to the contribution of Ga-P bond in 2Sb2P unit cell. On the other hand, in GaAsPSb supercell, the 1As1P2Sb unit cell with the lowest bond stretching energy should have made contribution to the LO+ line shape, but the formation probability of this cell is too low to have an effect on the spectra. So, we only can observe GaP-like LO mode in GaAsPSb Raman spectra.

並列關鍵字

GaPSb ； GaAsPSb ； bond distortion ； long-range order ； short-range disorder ； anharmonic interaction ； spatial correlation model ； valence force field model

參考文獻

[1] E. Lendvay, T. Gorog, L. Andor, L. Petras, and A. L. Toth, “A novel double heterostructure: the GaAs/GaPAsSb system,” J. Cryst. Growth 79, 928-934 (1986).

[2] M. J. Jou, Y. T. Cherng, H. R. Jen and G. B. Stringfellow, “OMVPE growth of the semiconductor alloys GaP1-xSbx and InP1-xSbx,” J. Cryst. Growth 93, 62-69 (1988).

[3] M. J. Jou, Y. T. Cherng, H. R. Jen and G. B. Stringfellow, “Organometallic vapor phase epitaxial growth of a new semiconductor alloy: GaP1-xSbx,” Appl. Phys. Lett. 52, 549 (1988).

[4] Lo et al., “Electron transport in a GaPSb film,” Nanoscale Research Letters 7, 640 (2012).

[5] H. Shimomura, T. Anan, and S. Sugou, “Growth of AlPSb and GaPSb on InP by gas-source molecular beam epitaxy,” J. Cryst. Growth 162, 121-125 (1996).

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磷銻化鎵與砷磷銻化鎵之結構特性研究

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