矽、鍺與銅銦鎵硒表面鈍化處理之研究

Surface Passivation of Silicon, Germanium, and Cu(In,Ga)Se2

徐禎婉(Chen-Wan Hsu)

指導教授 ： 劉致為

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.10582

摘要

本論文中，探討矽的表面鈍化處理和不同材料表面鈍化處理後的矽與鍺之光激發放光，以及含有表面鈍化層氧化鋁的銅銦鎵硒可增強光激發放光。
有效的鈍化處理存在於低界面陷阱密度和游離電荷的場效鈍化。氧化矽在高成長溫度900℃下因為有較少的界面陷阱密度，所以是有效的鈍化層，氧化鋁捕捉負電荷可提供場效鈍化，此外，非晶矽也可以有效控制游離電荷密度提供場效鈍化。有效的載子生命週期可用准穩態光電導(Quasi-steady-state photoconductance)技術量測。光激發放光強度和表面復合速率有關。非晶矽鈍化層在高溫退火結晶化後，因為有較大的能隙所以鈍化效果變差。GeO2長在鍺上後，光激發放光量測出用波長457nm的雷射光比和用波長671nm的雷射光，有相對較高的光強度。
銅銦鎵硒太陽能電池效率已經可高達19%以上，很多文獻已經研究利用光激發放光分析缺陷。銅銦鎵硒的放光特性和成分組成有極大的關聯，一般解釋銅銦鎵硒的放光頻譜有兩種轉移機制，一是DAP復合，即在低溫時的Ed能階到Ea能階的躍遷，二是BI復合，即在高溫下導電帶的電子到Ea能階的躍遷。透過模擬，我們可以連結表面復合速率和載子濃度的關係，而氧化鋁當銅銦鎵硒的鈍化層可有效減少界面缺陷，因此光激發放光增強。

關鍵字

表面鈍化 ； 表面復合速率 ； 載子生命週期 ； 銅銦鎵硒 ； 光激發放光

並列摘要

In this thesis, surface passivation of silicon, photoluminescence of silicon and germanium with various passivation layers, and enhancement of photoluminescence from Cu(In,Ga)Se2 with Al2O3 passivation are discussed.
The effective passivation needs low interface trap density at the interface between passivation layer and Si, and ionized charges for field effect passivation. The thermal oxide (SiO2) with low interface defect density seems most effective but requires high growth temperature (900 ℃). Al2O3 with trapped negative fixed charges can serve as the field effect passivation. Moreover, doped amorphous Si can also have the field effect passivation with the controlled ionized charge density. The effective lifetime is measured by quasi-steady-state photoconductance (QSSPC). Photoluminescence (PL) measurement is consistent with QSSPC. The dependence of PL intensity on surface recombination velocity is theoretically studied. The passivation of a-Si becomes less effective after crystallization at high temperature annealing, indicating the larger bandgap is necessary. The GeO2 passivation on Ge seems effective and relative light intensity with 457nm laser by pumping is a little stronger than 671nm.
CIGS solar cells have attained efficiencies above 19% and can be made with a number of different manufacturing techniques. Photoluminescence (PL) spectroscopy is a useful technique to analyze defects in semiconductor. Photoluminescent properties of such films depend strongly on their stoichiometry. The PL emission is explained in terms of two type transitions: donor–acceptor-pair (DAP) recombination at low temperatures and moderate excitation powers, and the band-impurity (BI) recombination involves electrons in conduction band to acceptor levels at high temperatures or high excitation power. Through the simulation we can connect with the relationship of surface recombination velocity and carrier concentration. Al2O3 seems effective passivation reduces interface defect of CIGS. Therefore, light intensity is enhancement from PL measurement.

並列關鍵字

surface passivation ； surface recombination velocity ； lifetime ； CIGS ； photoluminescence

參考文獻

參考文獻 [1] Daniel Macdonald, L. J. Geerligs, Appl. Phys. Lett. 85, 4061 (2004).

[2] B. Hoex, J. Schmidt, R. Bock, P. P. Altermatt, M. C. M. van de Sanden, and W. M. M. Kessels, Appl. Phys. Lett. 91, 112107 (2007).

[4] Hezel R, Jaeger K. Low temperature surface passivation of silicon for solar cells. Journal of the Electrochemical Society , 136, 518–523 (1989).

[6] A. G. Aberle, Crystalline Silicon Solar Cells: Advanced Surface Passivation and Analysis, The University of New South Wales, Sydney, Australia, 1999.

[1] A. G. Aberle, Crystalline Silicon Solar Cells: Advanced Surface Passivation and Analysis, The University of New South Wales, Sydney, Australia, 1999.