Table 2

The input parameters used to model the 2.4 μm epi-Si layer cell. Note that the quantities marked with superscript “a” have been measured, those marked with superscript “b” have been taken from the literature, and that marked with superscript “c”, supplied by the manufacturer. The other parameters and the interface defect densities have been extracted by simulation. In this case (2.4 μm cell), the defect density at the top N-a-Si:H/I-epi-Si interface is 1011 cm-2, while that at the rear I-epi-Si/P+-c-Si interface is 1012 cm-2. For the case of the 1.7 μm cell all parameters are the same as for the 2.4 μm cell, only the N-a-Si:H layer appears to be  ~16 nm from modelling (as explained in the text) and the rear interface defect density is higher: 1.35 × 1012 cm-2. However, for the 0.9 μm cell the defect density at both interfaces of the epi-Si layer had to be equal to 1012 cm-2 and the volume defect density 1.2 × 1016 cm-3. The charged and neutral capture cross-sections (σ) of these defect states, have been assumed to be one order of magnitude higher than the corresponding σ’s inside the volume of epi-Si for all cases, while a 0.5 μm region adjacent to the top DL is assumed to have σ’s intermediate between the two and a defect density twice that in the rest of the volume.

Parameters N-a-Si:H I-epitaxial Si P-c-Si

Thickness (μm)a 0.012 2.4 525
Mobility gap (Eμ) (eV) 1.8a 1.12a,b 1.12b
Doping density (cm 1.1 × 1019a 0 3.0 × 1018c
Electron affinity (eV)b 4.0 4.22 4.22
Eff. DOS in bands 2 × 1020 2.8 × 1019 2.8 × 1019
(cm-3) 2 × 1020 1.04 × 1019 1.04 × 1019
Charac. En. ED (EA) (eV)b 0.05 (0.03)
GD0, GA0 (cm-3 eV 4.0 × 1021
Elec. (hole) mobility 20 (4) 400 (125)a 300(100)a
(cm2/V S)
Gaussian defect den. (cm 6.0 × 1018a 1015 6.0 × 1017
Donor Gaussian peak pos 0.7 0.4 0.4 VB (eV)
Acceptor Gaussian peak pos 0.6 0.4 0.4 CB (eV)
Capture cross-sections (cm2)
mid-gap: charged (neutral) 10-14 (10-15) 10-16 (10-17) 4 × 10-17 (4 × 10-18)
tails: charged (neutral) 10-14 (10-15)

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