Properties of silicon films deposited under argon dilution
- PDF / 829,250 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 99 Downloads / 200 Views
Properties of silicon films deposited under argon dilution C. Longeaud1, D. Roy1, P. Chaudhuri2, N. Dutta Gupta2, P. Pratim Ray2, S. Vignoli3, R. Meaudre3, M. Meaudre3 and L. Saviot4. 1 Laboratoire de Génie Electrique de Paris (UMR 8507 CNRS), Supélec, Universités Paris VI et XI, Plateau de Moulon 91190, Gif sur Yvette, France. 2 Energy Research Unit, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700 032, India. 3 Département Physique des Matériaux (UMR 5586 CNRS), Université Lyon 1, 43 Bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France. 4 Laboratoire de Physico-Chimie des Matériaux Luminescents (UMR 5620 CNRS), Université Lyon 1, 43 Bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France. ABSTRACT Four series of samples, prepared at 250°C by decomposition of a mixture of silane and argon in a radio frequency powered deposition systems (rf-PECVD), have been studied. The dilution rates were 1 %, 1.5 %, 5 % and 10 % of silane in argon and the total pressure was 0.5 Torr for the first series and 0.2 Torr for the others. Structural and transport properties of the materials have been studied as function of power density. Structural studies show the transition from purely amorphous material towards microcrystalline material with increasing rf power density. The transport parameters were measured in the as-deposited, light-soaked and annealed states and compared to those obtained on state of the art material. The best material obtained is clearly device grade material. This study shows that argon dilution allows to tailor the material for a given application. INTRODUCTION Initial studies on dilution of silane (SiH4) with argon (Ar) for deposition of hydrogenated amorphous silicon (a-Si:H) by radio frequency powered plasma enhanced chemical vapour deposition (rf-PECVD) method resulted in materials with large structural inhomogeneity having poor optoelectronic properties [1]. Powder formation within argon diluted silane plasma was believed to be the main reason for the poor quality of the deposited film. However, recent studies have shown that excellent quality Si:H films may be obtained under the conditions of nanometre size powder formation within the plasma [2]. Beneficial effect of bombardment of the growing film by the Ar+ ions and Ar* metastables may also give rise to good quality material. Recently we observed that nanometre size heterogeneities within the films deposited by rf-PECVD of SiH4-Ar mixture may be controlled by varying the argon dilution level [3]. In this paper we report the study of transport properties of four different series of a-Si:H samples prepared at 250 °C by decomposition of SiH4-Ar mixture by RF-PECVD near the conditions of powder formation.
A23.1.1
SAMPLES AND EXPERIMENTS Four series of samples have been prepared at a substrate temperature of 250 °C by varying the proportions of SiH4 and Ar in two different PECVD systems. One series (SA series) was deposited in an ultra high vacuum multi chamber apparatus at a deposition pressure of 0.5 Torr and a dilution of
Data Loading...
