Feb 4, 2016

Effect of light germanium doping on thermal donors in Czochralski silicon wafers

In this paper, the effect of light Germanium (Ge-) doping on thermal donors (TDs) in Czochralski silicon (CZ-Si) has been investigated by four-point probe and low-temperatures Fourier transform infrared (FTIR) spectrometer. After 650 °C, 30 min annealing to eliminate the grown-in TDs, conventional CZ-Si and germanium-doped CZ-Si (GCZ-Si) samples were further subjected to isothermal annealing at about 450 °C to generate TDs. It was found that Ge-doping suppressed the formation of TDs. Moreover, the low temperature FTIR absorption spectra of the TDs in GCZ-Si were found to agree quite well with that of TDs in CZ-Si, which was not the case for the heavily Ge-doped silicon. Therefore, it is considered that the light Ge-doping suppresses the formation of TDs but does not affect the microscopic structure of TDs.


Debris-Free Rear-Side Picosecond Laser Ablation of Thin Germanium Wafers in Water with Ethanol


Picosecond laser cutting of fragile 150 μm thin germanium wafers (typically used for solar cell applications) in liquid results in debris-free surfaces
Liquid-assisted laser cutting is much better than air-assisted laser cutting in terms of recast, debris and cleanness of the resultant grooves
Laser cutting in ethanol-water mixtures result in better cut quality than those performed in pure water but lead to less cutting efficiency
Low repetition rate (10 kHz), mixed solution (1wt% ethanol in water) and moderate scanning speed (100 μm/s) are preferable for ultrafine high-quality debris-free cutting