Interplay between electrical transport properties of GeMn thin films and Ge substrates

Abstract

We present evidence that electrical transport studies of epitaxial p-type GeMn thin films fabricated on highresistivity Ge substrates are severely influenced by parallel conduction through the substrate, related to the large intrinsic conductivity of Ge due to its small band gap. Anomalous Hall measurements and large magnetoresistance effects are completely understood by taking a dominating substrate contribution as well as the measurement geometry into account. It is shown that substrate conduction persists also for well-conducting, degenerate, p-type thin films, giving rise to an effective two-layer conduction scheme. Using n-type Ge substrates, parallel conduction through the substrate can be reduced for the p-type epilayers, as a consequence of the emerging pn-interface junction. GeMn thin films fabricated on these substrates exhibit a negligible magnetoresistance effect. Our study underlines the importance of a thorough characterization and understanding of possible substrate contributions for electrical transport studies of GeMn thin films.

Components of strong magnetoresistance in Mn implanted Ge

“…11 and 12. Less exotic mechanism was suggested by Zhou et al 13 that pointed out that much of the phenomena, in particular nonmonotonous Hall angle, can be explained by parallel conduction of two charge carriers generated by, e.g., two-level Mn acceptors in Ge. Supporting evidence for the two-carrier transport, although in a different geometrical implementation, was demonstrated by Sircar et al 14 that showed that parallel conduction along a doped layer and Ge substrate can generate very large magnetoresistance and non-monotonic Hall effect remarkably similar to the previous GeMn data, also when non-magnetic GeB films were grown on top of Ge substrates. It was thus concluded that spectacular properties of GeMn systems are not a consequence of alloying of magnetic Mn with Ge but result from parallel conduction along thin conducting doped epilayer and thick resistive Ge substrate.…”

Spin-charge-coupled transverse resistance in an ambipolar conductor YH2-based Hall-bar structure with perpendicularly magnetized current-injection electrodes

“…As shown in figure 5, the slope of the linear B variation decreased upon removing the Pt capping layer. The influence of the Pt layer on the measurement can be evaluated using the following formula derived from a twolayer conduction model [38]:…”

Low Temperature Direct Bonding of Ge Chips with DBC Alumina Substrates using Ag Nanotwinned Films

“…Nevertheless, many researchers have reported on the superior properties of Ge substrates. Sircar et al described the electron transport properties of Ge substrates with epitaxial p-type GeMn thin films, which gives rise to an effective 2-layer conduction scheme [2].…”