Golovynskyi Sergii, Seravalli Luca, Datsenko Oleksandr, Kozak Oleksii, Kondratenko Serhiy V, Trevisi Giovanna, Frigeri Paola, Gombia Enos, Lavoryk Sergii R, Golovynska Iuliia, Ohulchanskyy Tymish Y, Qu Junle
College of Optoelectronic Engineering, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen, 518060, People's Republic of China.
Institute of Semiconductor Physics, National Academy of Sciences, Kyiv, 03028, Ukraine.
Nanoscale Res Lett. 2017 Oct 5;12(1):559. doi: 10.1186/s11671-017-2331-2.
The bipolar effect of GaAs substrate and nearby layers on photovoltage of vertical metamorphic InAs/InGaAs in comparison with pseudomorphic (conventional) InAs/GaAs quantum dot (QD) structures were studied. Both metamorphic and pseudomorphic structures were grown by molecular beam epitaxy, using bottom contacts at either the grown n -buffers or the GaAs substrate. The features related to QDs, wetting layers, and buffers have been identified in the photoelectric spectra of both the buffer-contacted structures, whereas the spectra of substrate-contacted samples showed the additional onset attributed to EL2 defect centers. The substrate-contacted samples demonstrated bipolar photovoltage; this was suggested to take place as a result of the competition between components related to QDs and their cladding layers with the substrate-related defects and deepest grown layer. No direct substrate effects were found in the spectra of the buffer-contacted structures. However, a notable negative influence of the n -GaAs buffer layer on the photovoltage and photoconductivity signal was observed in the InAs/InGaAs structure. Analyzing the obtained results and the performed calculations, we have been able to provide insights on the design of metamorphic QD structures, which can be useful for the development of novel efficient photonic devices.
研究了与赝晶（传统）InAs/GaAs量子点（QD）结构相比，GaAs衬底和附近层对垂直变质InAs/InGaAs光电压的双极效应。通过分子束外延生长变质和赝晶结构，在生长的n缓冲层或GaAs衬底处使用底部接触。在两种缓冲层接触结构的光电光谱中都识别出了与量子点、润湿层和缓冲层相关的特征，而衬底接触样品的光谱显示了归因于EL2缺陷中心的额外起始点。衬底接触样品表现出双极光电压；这被认为是由于与量子点及其包层相关的成分与与衬底相关的缺陷和最深生长层之间的竞争而发生的。在缓冲层接触结构的光谱中未发现直接的衬底效应。然而，在InAs/InGaAs结构中观察到n-GaAs缓冲层对光电压和光电导信号有显著的负面影响。通过分析获得的结果和进行的计算，我们能够为变质量子点结构的设计提供见解，这对新型高效光子器件的开发可能有用。
