Low temperature resistivity of heavily boron doped LPVCD polysilicon thin films

Abstract

Heavily boron δ-doped polysilicon samples were prepared by horizontal low-pressure chemical vapour deposition (LPCVD) at 750 °C for 1 h and were annealed at 1200 °C for 1 h. In this way, the samples with low sheet resistance down to 8.9 Ω sq−1, were obtained. The boron concentration was determined from the room temperature sheet resistance. The resistivity was measured from room temperatures down to 2 K. A T1/2 dependence of the conductivity in an unusually wide temperature interval, even up to 80 K was observed. Above 140 K, the resistivity can be described by the T3/2 dependence. The experimental results were analysed within the theories for the disordered metals and compared with the corresponding existing resistivity data.

Low-temperature transport properties of TaxN thin films (0.72 ⩽ x ⩽ 0.83)

“…where m can be negative as it is in some highly doped semiconductors [9,31], but in disordered metallic systems it is usually positive like the third term in equation (14). Plotting the transport data versus T 1/2 (figure 8) shows the presence of the T 1/2 term at the lowest temperatures.…”

“…The resistivity was then calculated by the following relation: ρ = R sq a. The experimental procedure with a comparison between the two described methods was recently used in investigations of Si : B thin films [9]. Independently, the resistivity was also measured on another cut sample but in the van der Pauw geometry.…”

“…With increasing temperature, inelastic scatterings appear which destroy the quantum coherence. If τ in τ e (9), an electron diffuses the distance…”

“…The theoretical relations are certainly oversimplified for application in a wide temperature range. For example, the relation in equation (9), τ in τ e or in might not be completely fulfilled at higher temperatures. This does not imply that there is no quantum coherence and thereby no localization at higher temperatures.…”