Page 9 - Carrier Recombination Activity and Structural Properties of Small-Angle Grain Boundaries in Multicrystalline Silicon

Jpn. J. Appl. Phys., Vol. 46, No. 10A (2007) EBIC contrast
J. CHEN and T. SEKIGUCHI
Contamination level Medium 20
Heavy
40 %
30

10
Light
5
Clean
0
Σ3 Σ3* Σ9 Σ27 R SA 2

Fig. 10. Classification of the EBIC contrast of GBs at 300 K with respect to GB character and contamination level (3–3 {111};

3 –3 with other planes).

As grown H-passivated Strong SA

EBIC_300 K

(a) (b)
Weak SA

EBIC_100 K Strong SA Weak SA

(c) (d) 400 µm

Fig. 11. EBIC images of SA-GBs in as-grown and H-passivated mc-Si.

at 100 K [Fig. 11(d)] changed significantly. First, the EBIC
contrast of all the SA-GBs is reduced. Second, all the
intragranular defects disappeared.
Figure 12 shows the EBIC contrast (at 100 K) of SA-GBs
before and after H passivation. The EBIC contrast of the Fig. 12. Low-temperature (100 K) EBIC contrast of SA-GBs in as-grown
weak SA was reduced from 25–30% to 5–10%, while that and H-passivated mc-Si. The strong SA and weak SA were denoted in
of the strong SA was reduced from 35–40% to 25–30%. Fig. 11(c).
The passivation efficiency was about 60–80% for the weak
SA but only 25–40% for the strong SA. As discussed in
section §3.1, the strong SA may be accompanied with a high contrast (<10%) at 300 K with the maximum contrast

density of dislocations (with strain) or impurity contami- appearing at 2 . EBIC results for artificial SA-GBs in
nation, which suppresses the efficiency of H passivation. The bonded Si showed a similar distribution of contrast with
strong SA are the most detrimental defects in mc-Si, since respect to the tilt angle. However, some special SA-GBs
they are easily decorated with impurities and are difficult to with a tilt angle of around 2–3 in mc-Si showed
passivate. particularly strong EBIC contrast of up to 30%, which
may originate from the high density of defects or the
4. Conclusions
impurity contamination. Contamination experiments sug-
The recombination activity of SA-GBs in mc-Si with gested that SA-GBs showed stronger impurity-gettering
respect to the intrinsic effect of the boundary structure (tilt ability than LA-GBs. H passivation could partially passivate
angle) and the extrinsic effect of impurity (Fe) contami- the electrically active defects at SA-GBs. It is concluded that
nation were studied using EBIC. In the clean mc-Si, general SA-GBs possess a high density of electrically active defects

SA-GBs with a tilt angle from 0 to 10 showed weak EBIC and are the most detrimental defects in mc-Si.
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