The interface of a-SiNx:H and Si: Linking the nano-scale structure to passivation quality

Author(s)

Machteld Lamers, Leif E. Hintzsche, Keith T. Butler, Per Erik Vullum, Changming Fang, Martijn Marsman, Gerald Jordan, John H. Harding, Georg Kresse, Arthur Weeber

Abstract

Surface passivation by hydrogenated amorphous silicon nitride (a-SiN_x:H)

is determined by the combined effect of two mechanisms: so-called

chemical passivation by reducing the density of interface states (D_it) and field-effect passivation as a result of the number of fixed charges (Q_f) at the interface with Si. These are related to the K defect center: ^*Si-N₃. Defects near the interface (in both Si as in a-SiN_x:H), modeled by force field Molecular Dynamics (MD) and ab initio Density Functional Theory (DFT), can be related to Q_f and D_it

measured experimentally using CV-MIS (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 a-SiN_x:H composition in the first 2 nm of the a-SiN_x:H

layer. At the c-Si 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 a-SiN_x: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 K-centers at the surface, which explains the

variation in Q_f and D_it that is found experimentally. Ab initio DFT studies of a-SiN_x:H (x=1.17) show that K-centers and Si atoms in distorted configuration, are the dominating defects resulting in a higher D_it. For lower x (x=1) the D_it caused by K-centers increases, which is observed experimentally too.

Organisation(s)

Computational Materials Physics

External organisation(s)

ECN Solar Energy, University of Sheffield, SINTEF The Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology (NTH)

Journal

Solar Energy Materials & Solar Cells

Volume

120

Pages

311-316

No. of pages

6

ISSN

0927-0248

DOI

https://doi.org/10.1016/j.solmat.2013.04.026

Publication date

01-2014

Peer reviewed

Yes

Austrian Fields of Science 2012

103025 Quantum mechanics, 103036 Theoretical physics, 103015 Condensed matter, 103009 Solid state physics

Keywords

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Renewable Energy, Sustainability and the Environment

Portal url

https://ucrisportal.univie.ac.at/en/publications/98771389-9c42-4ff1-ac88-eaac46bc23be