Excitons are promising candidates for generating superfluidity and Bose–Einstein condensation (BEC) in solid-state devices, but an enabling material platform with in-built band structure advantages and scaling compatibility with industrial semiconductor technology is lacking. Here we predict that spatially indirect excitons in a lattice-matched strained Si/Ge bilayer embedded into a germanium-rich SiGe crystal would lead to observable mass-imbalanced electron–hole superfluidity and BEC. Holes would be confined in a compressively strained Ge quantum well and electrons in a lattice-matched tensile strained Si quantum well. We envision a device architecture that does not require an insulating barrier at the Si/Ge interface, since this interface offers a type II band alignment. Thus the electrons and holes can be kept very close but strictly separate, strengthening the electron–hole pairing attraction while preventing fast electron–hole recombination. The band alignment also allows a one-step procedure for making independent contacts to the electron and hole layers, overcoming a significant obstacle to device fabrication. We predict superfluidity at experimentally accessible temperatures of a few Kelvin and carrier densities up to ~6 × 10¹⁰ cm⁻², while the large imbalance of the electron and hole effective masses can lead to exotic superfluid phases.

激子是在固态器件中产生超流动性和玻色-爱因斯坦凝聚（BEC）的有前途的候选者，但缺乏具有内置能带结构优势和与工业半导体技术的规模兼容性的支持性材料平台。在这里，我们预测嵌入富含锗的SiGe晶体中晶格匹配的应变Si / Ge双层中的空间间接激子将导致可观察到的质量失衡的电子空穴超流动性和BEC。空穴将被限制在压缩应变的Ge量子阱中，而电子将被限制在晶格匹配的拉伸应变Si量子阱中。我们设想了一种在Si / Ge接口上不需要绝缘势垒的设备架构，因为该接口可提供II型能带对准。因此，电子和空穴可以保持非常接近但严格分开，在防止电子-空穴快速复合的同时，增强了电子-空穴对的吸引力。带对准还允许一步步骤来独立地接触电子层和空穴层，从而克服了器件制造的重大障碍。我们预测在几个开尔文的实验可及温度下超流动性，并且载流子密度可达〜6×10¹⁰  cm ^-2，而电子和空穴的有效质量的巨大失衡可能导致奇特的超流体相。