Derk L. Bätzner

Lateral Si/SiO2 quantum well solar cells

The photovoltaic properties of Si∕SiO2 multiple quantum wells (QWs) embedded in lateral Schottky contacts are investigated. The QWs were fabricated by remote plasma enhanced chemical vapor deposition. By subsequent rapid thermal annealing, the two-dimensional Si layers are partially recrystallized, which gives rise to distinct quantum confinement effects. Although the current extraction along the quantum layers is hampered by the incomplete recrystallization, the data collected define the route to optimized Si based QW solar cells.

Confinement and transport in silicon based quantum structures

Crystallized Si QWs embedded between SiO<inf>2</inf> barrier layers were fabricated by remote plasma enhanced chemical vapor deposition of Si/SiO<inf>2</inf> and Si/SiO<inf>x</inf> stacks and subsequent high temperature annealing. Using SiO<inf>x</inf> instead of SiO<inf>2</inf> strongly enhances the overall crystallinity and the nanocrystallite size of the Si QWs. The phase separation of the SiO<inf>x</inf> into Si and SiO<inf>2</inf> increases the thickness of the Si QWs and yields thin SiO<inf>2</inf> barriers. Photoluminescence measurements on annealed stacks showed a quantum confinement of carriers within the Si QWs. The high degree of crystallization and the decrease of SiO<inf>2</inf> barrier height and thickness as well as possible shunting between adjacent Si layers improve the conductivity of annealed Si/SiO<inf>x</inf> stacks by up to seven orders of magnitude compared to Si/SiO<inf>2</inf> stacks.