Si/SiO2 multiple quantum wells for all silicon tandem cells: Conductivity and photocurrent measurements

Si/SiO2 multiple quantum wells (QWs) are fabricated by remote plasma enhanced chemical vapor deposition and subsequent rapid thermal annealing. The deposited QWs show strong carrier confinement resulting in effective band gap energies of up to 1.6 eV in 1 nm thick Si wells. The electrical transport characteristics of the QWs are assessed by current voltage measurements in vertical (perpendicular to the Si/SiO2 interfaces) and lateral (parallel to the interfaces) direction. These measurements show a four orders of magnitude increased conductivity in lateral direction compared to QWs with vertical contacts. From lateral photoconductivity measurements mobility lifetime products are derived as a function of QW thickness.