Photovoltaics

A DEEP LEVEL TRANSIENT STUDY OF IMPURITY CENTRES IN MICROCRYSTALLINE SILICON OBTAINED BY HOT-WIRE CHEMICAL VAPOUR DEPOSITION

V. Schlosser, A. Breymesser
Institut für Materialphysik der Universität Wien
A-1090 Wien, Strudlhofgasse 4, Austria, phone: (+43 1) 586 34 0927, e-mail: viktor.schlosser@univie.ac.at
D. Soler, M. Fonrodona, C. Voz, J. Bertomeu
Departament de Fisica Aplicada i Optica, Universitat de Barcelona
E-08208 Barcelona, Av. Diagonal 647, Spain.

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ABSTRACT:

We have investigated diode structures of microcrystalline silicon, deposited by hot-wire chemical vapour deposition, by means of the complex differential AC conductivity. An equivalent circuit model taking into account the two contributions to the conductance arising from the crystalline and the noncrystalline phase in the silicon films was used to derive information about the defect distribution in the microcrystalline silicon devices. The influence of slightly changing preparation conditions on the electrical behaviour of the samples was mainly caused by variations in the den-sity of surface states at the crystalline grains. A substrate temperature of 230 °C during deposition was leading to a smaller contribution of the noncrystalline phase to the conductivity than observed for samples deposited at 200 °C. Changing the filament temperature from 1600 °C to 1800 °C reduces the uncompensated electrically active surface state density.

Keywords: Micro Crystalline Si - 1: Defect Density - 2: Capacitance - 3