Direct measurement of Urbach tail and gap state absorption in CuGaSe2 thin films by photothermal deflection spectroscopy and the constant photocurrent method
Direct measurement of Urbach tail and gap state absorption in CuGaSe2 thin films by photothermal deflection spectroscopy and the constant photocurrent method
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DOI：
10.1063/1.1501745
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发表时间：
2002-08
影响因子：
3.2
通讯作者：
A. Meeder;D. F. Marrón;A. Rumberg;M. Lux‐Steiner;V. Chu;J. Conde
中科院分区：
文献类型：
--
作者：
A. Meeder;D. F. Marrón;A. Rumberg;M. Lux‐Steiner;V. Chu;J. Conde
研究了光热偏转光谱 (PDS) 和恒定光电流法 (CPM) 在化学气相沉积和物理气相沉积 CuGaSe2 (CGSe) 薄膜中的适用性。薄膜的直接带隙能量、乌尔巴赫尾宽度、体积和表面缺陷密度的工艺相关变化作为成分的函数给出。发现 PDS 和 CPM 吸收光谱存在超过一个数量级的差异。使用 PDS 和 CPM 分析的标准非晶硅理论，在器件质量的薄膜中发现了由缺陷丰富的近表面层和缺陷较少的体层组成的两层系统。作为生长过程第二阶段的 Ga+Se 退火步骤带来的光学改进导致体缺陷密度降低，而近表面缺陷密度保持不变。
The applicability of photothermal deflection spectroscopy (PDS) and the constant photocurrent method (CPM) to chemical vapor deposited and physical vapor deposited CuGaSe2 (CGSe) thin films is investigated. Process dependent variations in direct band-gap energies, Urbach tail widths, bulk and surface defect densities of the films are given as a function of composition. Differences in the PDS and CPM absorption spectra of more than one order of magnitude are found. Using the standard a-Si theory of PDS and CPM analysis, a two-layer system consisting of a defect-rich near-surface layer and a less defective bulk layer is found in device-quality films. Optical improvements due to the Ga+Se annealing step as a second stage of the growth process result in a reduced bulk defect density while the near-surface defect density remains unchanged.