Titel:

The interface of aSiNx:H and Si: Linking the nanoscale structure to passivation quality


Auteur(s):

Lamers, M.W.P.E.; Hintzsche, L.E.; Butler, K.T.; Vullum, P.E.; Fang, C.M.; Marsman, M.; Jordan, G.; Harding, J.H.; Kresse, G.; Weeber, A.W.


Gepubliceerd door:

Publicatie datum:

ECN
Zonneenergie

2852013


ECN publicatienummer:

Publicatie type:

ECNW13018

Artikel wetenschap tijdschrift


Aantal pagina's:


6


Gepubliceerd in: Solar Energy Materials & Solar Cells (Elsevier), , 2014, Vol.120, p.311316.
Samenvatting:
Surface passivation by hydrogenated amorphous silicon nitride (aSiNx:H)is determined by the combined effect of two mechanisms: socalled chemical passivation by reducing the density of
interface states (Dit) and ?eldeffect passivation as a result of the number of ?xed charges Qf)at the interface with Si. These are related to the K defect center: *SiN3. Defects near the
interface (in both Si as in aSiNx:H), modeled by force ?eld Molecular Dynamics MD)and ab
initio Density Functional Theory (DFT), can be related to Qf and Dit measured experimentally
using CVMIS (Capacitance–Voltage Metal–Insulator– Semiconductor). The compositional build up
at the interface as is determined by HRTEM High Resolution Transmission Electron Microscopy) and modeled by MD corresponds to each other; a gradual change from Si to the bulk aSiNx:H composition in the ?rst 2 nm of the aSiNx:H layer. At the cSi side a highly distorted
layer (about 1–3 nm) caused by the insertion of N and/or H is found. The insertion and
adhesion of N into and at the Si surface is called nitridation and can be altered by using a NH3 plasma prior to aSiNx:H deposition. HRTEM image analysis shows that by varying the nitridation of the Si surface the amount and penetration depth of N inside the Si surface is altered. Using MD modeling, it is shown that this process changes the amount of Kcenters at the surface, which explains the variation in Qf and Dit that is found experimentally. Ab initio DFT studies of aSiNx:H (x ¼ 1.17) show that Kcenters and Si atoms in distorted con?guration, are the dominating defects resulting in a higher Dit. For lower x (x ¼ 1) the Dit caused by Kcenters increases, which is observed experimentally too.
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