表面奈米結構對矽發光特性之影響

Influence of Surface Nanostructure on Silicon Light Emission

許書嘉(Chu-Chia Shiu)

指導教授 ： 林清富

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00925

摘要

本論文研究矽奈米結構對金屬-氧化層-矽基板(MOS)發光元件的發光特性。利用二氧化矽奈米粒子作為氧化層的MOS發光元件，提高了矽發光效率。低溫光激發光頻譜的量測中，發現二氧化矽奈米粒子旋塗在矽基板上減少了其發光的熱消散效應(thermal quenching)，使得發光效率提高一個數量級以上，且其效應隨著二氧化矽奈米粒子的尺寸縮小而越明顯。透過少數載子生命週期的探討，發現二氧化矽奈米粒子並未對矽基板產生破壞，矽基板仍然維持高品質，即仍然具有長的少數載子生命週期，因此降低了非放光性復合(nonradiative recombination)。此外，矽基板表面受到二氧化矽奈米粒子和氧化作用的影響，表面呈現凹凸起伏的奈米結構，載子被侷限在這些結構之中，更進一步減少了載子碰到缺陷而造成的非放光性復合，所以這層二氧化矽奈米粒子有助於減少表面的非放光復合機制(surface recombination velocity)，造成發光效率的提升。
為了探討矽奈米結構的形成和其效應，我們也利用雷射輔助直接壓印(Laser assisted direct imprint)製作矽基板表面的奈米結構，成功的製作出30nm的柱狀結構以及30nm的孔洞結構。石英模的製作方面，利用液態金屬凝聚的現象讓石英片上的金薄膜形成30nm左右的金奈米粒子，利用這層30nm的金奈米粒子當作遮罩，乾蝕刻得到直徑30nm高的石英柱結構，在矽基板上壓印出相似的柱狀結構。30nm的孔洞結構則是利用二氧化矽奈米粒子作為壓印的模所得到的結構，其製程較利用石英模壓印的方式簡單。利用少數在子生命週期來檢驗壓印後的矽基板品質，其載子生命週期約為200us，比乾蝕刻製作奈米結構的載子生命週期低於50us高許多，預期雷射輔助直接壓印的矽奈米結構對矽發光元件的發光效率會有所助益。

關鍵字

矽 ； 矽發光 ； 奈米結構 ； 雷射壓印

並列摘要

The thesis is about influence of surface nanostructure on silicon light emission. Using silicon dioxide nanoparticles as oxide layer in metal-oxide-silicon light emission diode would enhance silicon light emission efficiency. In low temperature photoluminescence spectral measurement, SiO2 nanoparticles reduced thermal quenching effect of light emission and the efficiency was higher than pure silicon about one order of magnitude. The effect was more obvious as the decrease of the size of SiO2 nanoparticles. Through minority carrier lifetime, we found SiO2 nanoparticles did not destroy silicon quality and it still had long minority carrier lifetime. It means silicon had lower nonradiative recombination. Moreover, the surface of silicon substrate would become rough due to SiO2 nanoparticles and oxidation effect. The surface roughness would cause carrier confinement and reduce nonradiative recombination due to defect in silicon crystal. Therefore, we thought SiO2 nanoparticles help reduce surface nonradiative recombination and result in light emission efficiency enhancement.
To study about the effect of silicon nanostructure, we used laser-assisted direct imprint(LADI) to fabricate silicon surface nanostructure. We could fabricate 30nm nanorods and 30nm holes on silicon surface. In fabrication of imprint quartz mold, we fabricated 30nm gold nanoparticles on quartz as etching mask and use dry etching to form quartz mold. Then we could fabricate the same structure by LADI. We also used SiO2 nanoparticles as imprint mold to fabricate 30nm holes on silicon surface. The process is simpler than using quartz mold. In minority carrier lifetime measurement, the lifetime was decreased to 200us. It is higher than the structure fabricated by dry etching. We expected silicon nanostructure fabricated by LADI will help silicon light emission.

並列關鍵字

silicon ； Si LED ； nanostructure ； LADI

參考文獻

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