Investigations of the electron transport behavior in microcrystalline Si films Sanjay K. Ram a , Satyendra Kumar a, * ,R egis Vanderhaghen b , P. Roca i Cabarrocas b a DepartmentofPhysics,IndianInstituteofTechnologyKanpur,Kanpur208016,India b LPICM,UMR7647–CNRS–EcolePolytechnique,Palaiseaucedex91128,France Abstract Fully crystallized dense lc-Si:H films with no trace of amorphous silicon have been obtained on glass substrates by standard rf glow discharge plasma CVD technique using a mixture of SiF 4 , Ar and H 2 at 200 °C. Temperature de- pendence of the dark conductivity (r d ) has been measured from 20 to 440 K on samples having different thicknesses. Above room temperature (300–440 K), the carrier transport is found to be thermally activated with a single activation energy.Atlowtemperature(300–80K)thethickerfilms(> 500 nm)showtunnelingofcarriersthroughbarrierssimilar towhatisobservedingranularmetals.Thinnersamplesexhibitacontinuousbendinginthe r d atlowtemperaturesthat has been explained in terms of the Meyer–Neldel rule. Results can be understood in terms of an increased degree of disorder in thinner samples. Ó 2002 Elsevier Science B.V. All rights reserved. PACS: 72.80.N; 73.61; 73.63.)b; 73.50 1. Introduction Plasma-deposited hydrogenated microcrystal- line silicon (lc-Si:H) thin films are gaining im- portance for large area electronic devices such as solar cells, thin film transistors (TFTs) based flat panel displays, and sensors. Large carrier mobility [1] and good stability are very attractive for TFTs [2]. However, plasma-deposited lc-Si:H is inher- ently a heterogeneous material. Understanding carriertransportinsuchasystemisundoubtedlya challenging task. Though there are several reports on the electronic transport in doped lc-Si:H [3,4], little attention is paid to the carrier transport in undoped lc-Si:H [5–7]. Often, transport behavior in lc-Si:H is treated analogous to that in a-Si:H, assuming it to be a homogeneous system [8]. In doped lc-Si:H films a Meyer–Neldel relationship (MNR) is found with parameters as obtained in a-Si:H [9]. The effect was explained in terms of a statistical shift of the Fermi level due to the band- tail states, as in a-Si:H. On the other hand, at- tempts are made to understand transport affected by the grain boundaries (GB) in a heterogeneous system [4]. In this case, a knowledge of band edge discontinuities between crystalline grains and amorphous Si tissue is required. Further, Zhou Journal of Non-Crystalline Solids 299–302 (2002) 411–415 www.elsevier.com/locate/jnoncrysol * Corresponding author. Tel.: +91-512 597 654; fax: +91-512 590 914. E-mailaddress: satyen@iitk.ac.in (S. Kumar). 0022-3093/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S0022-3093(01)00955-3