Afalla Jessica, Prieto Elizabeth Ann, Husay Horace Andrew, Gonzales Karl Cedric, Catindig Gerald, Abulikemu Aizitiaili, Somintac Armando, Salvador Arnel, Estacio Elmer, Tani Masahiko, Hase Muneaki
Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Japan.
National Institute of Physics, University of the Philippines Diliman, Quezon City, Philippines.
J Phys Condens Matter. 2021 Jun 16;33(31). doi: 10.1088/1361-648X/ac04cc.
Epitaxial low temperature grown GaAs (LT-GaAs) on silicon (LT-GaAs/Si) has the potential for terahertz (THz) photoconductive antenna applications. However, crystalline, optical and electrical properties of heteroepitaxial grown LT-GaAs/Si can be very different from those grown on semi-insulating GaAs substrates ('reference'). In this study, we investigate optical properties of an epitaxial grown LT-GaAs/Si sample, compared to a reference grown under the same substrate temperature, and with the same layer thickness. Anti-phase domains and some crystal misorientation are present in the LT-GaAs/Si. From coherent phonon spectroscopy, the intrinsic carrier densities are estimated to be 10 cmfor either sample. Strong plasmon damping is also observed. Carrier dynamics, measured by time-resolved THz spectroscopy at high excitation fluence, reveals markedly different responses between samples. Below saturation, both samples exhibit the desired fast response. Under optical fluences ⩾54J cm, the reference LT-GaAs layer shows saturation of electron trapping states leading to non-exponential behavior, but the LT-GaAs/Si maintains a double exponential decay. The difference is attributed to the formation of As-As and Ga-Ga bonds during the heteroepitaxial growth of LT-GaAs/Si, effectively leading to a much lower density of As-related electron traps.
硅上的外延低温生长砷化镓（LT-GaAs/Si）在太赫兹（THz）光电导天线应用方面具有潜力。然而，异质外延生长的LT-GaAs/Si的晶体、光学和电学性质可能与在半绝缘砷化镓衬底上生长的那些性质（“参考”）有很大不同。在本研究中，我们研究了外延生长的LT-GaAs/Si样品的光学性质，并与在相同衬底温度下、具有相同层厚的参考样品进行了比较。LT-GaAs/Si中存在反相畴和一些晶体取向错误。通过相干声子光谱，估计两个样品的本征载流子密度均为10 cm 。还观察到强烈的等离子体阻尼。在高激发通量下通过时间分辨太赫兹光谱测量的载流子动力学揭示了样品之间明显不同的响应。在饱和以下，两个样品都表现出所需的快速响应。在光通量⩾54J cm 时，参考LT-GaAs层显示出电子俘获态的饱和，导致非指数行为，但LT-GaAs/Si保持双指数衰减。这种差异归因于LT-GaAs/Si异质外延生长过程中As-As和Ga-Ga键的形成，有效地导致与As相关的电子陷阱密度低得多。
