Caractérisation physicochimique et électronique de la structure Pt–a-Si: H–c-Si(n)

Abstract

Infrared absorption spectra, and electrical measurements I(V, T) and C(V) at 100 Hz of the Pt–a-Si:H–c-Si structure are presented. The thickness, d, of the hydrogenated amorphous silicium, a-Si:H, varies between 4800 and 180 Å(1 Å = 10−10 m). Infrared absorption measurements on a-Si:H show that with the decrease in d there is an increase in the number of defects and the hydrogen concentration on Si-H sites. The electrical results I(V, T) show a Schottky-like structure whose ideality factor increases with decreasing T, but remains limited even for small values of d (1.4 at 300 K for d = 180 Å). Two potential barriers are also deduced: at high temperature [Formula: see text] and is independent of d. This barrier is attributed to the Pt–a-Si:H interface. At low temperature, [Formula: see text] increases from 0.23 to 0.5 eV as d decreases from 2400 to 180 Å. This barrier is attributed to the a-Si = H–c-Si, interface, the transport in a-Si:H taking place by tunnelling between localized states. The C(V) measurements allow the separation between the c-Si and the a-Si:H responses. Above 100 kHz, there is no response from a-Si:H, which behaves then as a dielectric. The electrostatic potential drop in c-Si is deduced as a function of the applied voltage V for each value of d. A positive electrostatic potential is found when V = 0 for d ≤ 500 Å.[Journal translation]