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.

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

Highlights

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Picosecond laser cutting of fragile 150 μm thin germanium wafers (typically used for solar cell applications) in liquid results in debris-free surfaces
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Liquid-assisted laser cutting is much better than air-assisted laser cutting in terms of recast, debris and cleanness of the resultant grooves
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Laser cutting in ethanol-water mixtures result in better cut quality than those performed in pure water but lead to less cutting efficiency
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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

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