Illuminating Trap Density Trends in Amorphous Oxide Semiconductors with Ultrabroadband Photoconduction
Illuminating Trap Density Trends in Amorphous Oxide Semiconductors with Ultrabroadband Photoconduction
复制标题
DOI：
10.1002/adfm.202300742
复制
发表时间：
2023-01
影响因子：
19
通讯作者：
G. Mattson;Kyle T. Vogt;J. Wager;M. Graham
中科院分区：
文献类型：
--
作者：
G. Mattson;Kyle T. Vogt;J. Wager;M. Graham
在不同的生长和器件工艺条件下，超宽带光导(UBPC)揭示了非晶态氧化物半导体薄膜晶体管(TFT)的缺陷态密度(DO)的强烈演化趋势。跨越非晶态InGaZnOx(a-IGZO)的宽带隙，UBPC发现了7个氧深施主空位峰，它们是通过与光致发光发射峰的能量匹配而独立确认的。来自15种不同类型的a-IGZO TFT的子隙DO都产生了相似的DO，只是只有后沟道刻蚀TFT在导带迁移率边缘以下2.2 eV处有一个很深的受主峰。这种深受主很可能是锌空位，当采用TFT湿法刻蚀时，陷阱密度增加了5-6倍。对于等离子体暴露引起的主动通道处理损伤的TFT，某些DoS峰被强烈地增强。当Ar注入和He等离子体处理损伤相似时，Ar等离子体产生更多的无序，表现为≈价带乌尔巴赫能量增加2倍，深氧空位陷阱密度增加两个数量级。改变a-IGZO的生长条件也会影响DO，与摩尔比为1：1：1的a-IGZO TFT相比，富锌TFT的电学性能要差得多，这是因为前者的氧空位陷阱密度比∼大10倍。最后，发现氢在非晶态铟锡镓锌氧化物薄膜晶体管中起施主作用。
Under varying growth and device processing conditions, ultrabroadband photoconduction (UBPC) reveals strongly evolving trends in the defect density of states (DoS) for amorphous oxide semiconductor thin‐film transistors (TFTs). Spanning the wide bandgap of amorphous InGaZnOx (a‐IGZO), UBPC identifies seven oxygen deep donor vacancy peaks that are independently confirmed by energetically matching to photoluminescence emission peaks. The subgap DoS from 15 different types of a‐IGZO TFTs all yield similar DoS, except only back‐channel etch TFTs can have a deep acceptor peak seen at 2.2 eV below the conduction band mobility edge. This deep acceptor is likely a zinc vacancy, evidenced by trap density which becomes 5‐6× larger when TFT wet‐etch methods are employed. Certain DoS peaks are strongly enhanced for TFTs with active channel processing damage caused from plasma exposure. While Ar implantation and He plasma processing damage are similar, Ar plasma yields more disorder showing a ≈2 × larger valence‐band Urbach energy, and two orders of magnitude increase in the deep oxygen vacancy trap density. Changing the growth conditions of a‐IGZO also impacts the DoS, with zinc‐rich TFTs showing much poorer electrical performance compared to 1:1:1 molar ratio a‐IGZO TFTs owing to the former having a ∼10 × larger oxygen vacancy trap density. Finally, hydrogen is found to behave as a donor in amorphous indium tin gallium zinc oxide TFTs.