Large-grain polycrystalline silicon films with low intragranular defect density by low-temperature solid-phase crystallization without underlying oxide
The solid-phase crystallization of an amorphous silicon film to polycrystalline silicon by a low-temperature (⩽600 °C) furnace anneal has been investigated in a suspended cantilever structure without underlying silicon oxide by transmission electron microscopy and Raman spectroscopy. The grain size of polysilicon increases up to ∼3.0 μm and the density of intragranular defects decreases one order of magnitude in the samples without underlying oxide, compared with those with underlying oxide. The main reasons for the high quality of the suspended structures are thought to be due to the lower stress in the films during crystallization and a reduced grain nucleation rate.
Laser induced defects in silicon solar cells and laser annealing
High power lasers are attractive for low-cost solar cell fabrication. However, laser process can generate crystal lattice defects that would decrease the photovoltaic efficiency. This study examines the effect of long pulsed laser annealing for improving the cell efficiency and results are compared with the short pulsed laser and furnace annealing. Results show that long pulsed laser annealing is effective in increasing the short circuit current for laser processed back-contact solar cells. The short circuit current increases by 1.5 times indicating the removal of defects. Laser annealing would allow widespread use of laser processing method for low-cost solar cell manufacturing.
Amorphous‐Si/crystalline‐Si facet formation during Si solid‐phase epitaxy near Si/SiO2 boundary
Amorphous‐Si (a‐Si)/crystalline‐Si (c‐Si) interface facet formation was found during Si solid‐phase epitaxy (SPE) near the Si/SiO2 boundary. A (110) facet is formed during (010)b‐[100]SPE (SPE growth in the [100] direction and near the (010) boundary between a‐Si and SiO2). A (111) facet is formed during (011)b‐[100]SPE. The facet formation is explained with an atomistic model wherein an a‐Si atom must complete at least two undistorted bonds to attain SPE growth, and the boundary condition wherein an a‐Si atom cannot form undistorted bond to Si/SiO2 boundary.