Experimental Characterization and Modeling of High Hole Mobility GeSn Quantum Wells: The Role of Alloy Disorder...

Understanding mechanisms influencing electrical transport in material systems not only provides a scientific explanation for observed behavior but also offers insight into ways to enhance transport in devices. This study reports experimental hole mobility of $8\times {10}^4\hspace{0.17em}{\mathrm{cm}}^2\hspace{0.17em}{V}^{-1}\hspace{0.17em}{s}^{-1}$ in a Ge_0.92Sn_0.08, the highest recorded mobility for the GeSn system. A study of the material's quality is presented using structural and electrical characterization techniques, with transport data being supported by simulations using an extensive modeling framework. Quantum Hall measurements further indicate the material's high quality and potential spintronic applications, with extracted values of $0.0689m_0$ and $13.6$ for the effective mass and effective g-factor, respectively. It is observed that transport is limited by alloy disorder scattering at cryogenic temperatures. A comparative study between the presented structure and similar quantum well heterostructures revealed that the difference in hole mobilities is captured by a disparity in the reduced nominal alloy disorder scattering potential ( $\Delta U_{\mathrm{alloy}}$ = 0.8 eV), that is lower than the value of a fully random alloy ( $\Delta U_{\mathrm{alloy}}$  = 1.4-1.7 eV) potential. The difference in $\Delta U_{\mathrm{alloy}}$ suggests that heterostructures with similar geometries and alloy compositions can have different alloy disorder scattering, implying that an underlying mechanism, such as short-range order, may be responsible and warrants further investigation.