TY - JOUR
T1 - Electron–hole superfluidity in strained Si/Ge type II heterojunctions
AU - Conti, Sara
AU - Saberi-Pouya, Samira
AU - Perali, Andrea
AU - Virgilio, Michele
AU - Peeters, François M.
AU - Hamilton, Alexander R.
AU - Scappucci, Giordano
AU - Neilson, David
PY - 2021
Y1 - 2021
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85104969153&partnerID=8YFLogxK
U2 - 10.1038/s41535-021-00344-3
DO - 10.1038/s41535-021-00344-3
M3 - Article
AN - SCOPUS:85104969153
SN - 2397-4648
VL - 6
JO - npj Quantum Materials
JF - npj Quantum Materials
IS - 1
M1 - 41
ER -