氮化銦奈米柱陣列之載子動力學

Carrier dynamics of InN nanorod arrays

游至正(Chih-Cheng Yu)

指導教授 ： 安惠榮

國立交通大學/電機學院/光電工程系所/碩士(2011年)

https://doi.org/10.6842/NCTU.2011.01066

摘要

Indium nitride (InN) with a narrow direct band gap has superior electronic transport properties over other group-III nitrides and it makes InN attractive for applications such as high-frequency electronic devices, near-infrared optoelectronics, and high-efficiency solar cells. With the rapid down-sizing of electronic and photonic device dimensions, understanding of the carrier transportation in nanoscale materials becomes crucial. In this thesis, we report the ultrafast carrier dynamics of vertically aligned InN nanorod arrays grown by molecular-beam epitaxy on Si (111) substrates. We employ ultrafast optical spectroscopy at a wide range of probe wavelengths (800 nm – 1600 nm) to understand the absorption/relaxation process of nanorods with different rod height, diameter, and rod density. The band-filling effect dominant absorption process is observed for nanorods, while the band-gap renormalization effect is dominant in epilayer. Typically, band-gap renormalization is significant in high carrier density and then band-filling dominant absorption in InN nanorods indicates smaller carrier density than in epilayer, due to less efficient absorption limited by the size of nanorods. Polarization-dependent transient reflectivity responses in nanorods shows that carrier lifetimes along parallel and perpendicular directions to the axis of nanorods are different only for small-diameter nanorods, implying that the carrier confinement can occur in the nanorods with the diameter comparable to theirs diffusion length.

關鍵字

氮化銦 ； 載子動力學 ； 奈米柱

並列摘要

Indium nitride (InN) with a narrow direct band gap has superior electronic transport properties over other group-III nitrides and it makes InN attractive for applications such as high-frequency electronic devices, near-infrared optoelectronics, and high-efficiency solar cells. With the rapid down-sizing of electronic and photonic device dimensions, understanding of the carrier transportation in nanoscale materials becomes crucial. In this thesis, we report the ultrafast carrier dynamics of vertically aligned InN nanorod arrays grown by molecular-beam epitaxy on Si (111) substrates. We employ ultrafast optical spectroscopy at a wide range of probe wavelengths (800 nm – 1600 nm) to understand the absorption/relaxation process of nanorods with different rod height, diameter, and rod density. The band-filling effect dominant absorption process is observed for nanorods, while the band-gap renormalization effect is dominant in epilayer. Typically, band-gap renormalization is significant in high carrier density and then band-filling dominant absorption in InN nanorods indicates smaller carrier density than in epilayer, due to less efficient absorption limited by the size of nanorods. Polarization-dependent transient reflectivity responses in nanorods shows that carrier lifetimes along parallel and perpendicular directions to the axis of nanorods are different only for small-diameter nanorods, implying that the carrier confinement can occur in the nanorods with the diameter comparable to theirs diffusion length.

並列關鍵字

InN ； carrier dynamic ； nanorod

參考文獻

[2] 吳忠霖/果尚志, "三族氮化物異質接面之晶格與能帶結構," 物理雙月刊(三十六卷六期), 2008年12月.

[3] F. Chen, et al., "Hole transport and carrier lifetime in InN epilayers," Applied Physics Letters, vol. 87, pp. 212104-3, 2005.

[4] D. Zanato and et al., "Hot electron cooling rates via the emission of LO-phonons in InN," Semiconductor Science and Technology, vol. 19, p. 1024, 2004.

[5] F. Chen, et al., "Time-resolved spectroscopy of recombination and relaxation dynamics in InN," Applied Physics Letters, vol. 83, pp. 4984-4986, Dec 2003.

[6] J. W. Pomeroy, et al., "Phonon lifetimes and phonon decay in InN," Applied Physics Letters, vol. 86, pp. 223501-3, 2005.