Impurity Conduction Observed in Al-Doped 6H-SiC

Abstract

6H-SiC single crystals doped with aluminum acceptors at different concentrations were investigated with admittance spectroscopy and Hall effect. Thermally activated impurity conduction was observed at temperatures below 160K. The activation energy of 17meV was obtained from admittance spectroscopy as well as from temperature-dependent resistivity measurements. The Hall coefficient showed a sign reversal in the temperature range where hopping conduction dominates.

Anomalous charge carrier transport phenomena in highly aluminum doped SiC

“…Samples with specific resistivities between 1.22 Ωcm and 0.25 Ωcm at room temperature show a more or less abrupt change of slopes in the resistivity curves. This is in accordance with the behavior reported in [4]. Two regimes with different transport mechanisms can be discerned: In the regime with a steep slope at high temperatures hole conduction is the prominent mechanism of transport while the regime at low temperatures is dominated by impurity conduction.…”

“…A maximum and a change in sign were reported for the temperature dependence of the Hall constant [4]. Thus, three regimes were deduced: (i) Hole conduction outweighs impurity conduction.…”

“…), which was attributed to alternative charge carrier transport mechanisms [3]. Impurity conduction at low temperatures has already been reported for SiC with medium aluminum concentrations ([Al] ≈ 3 · 10 18 cm -3 ) [4]. In this study, investigations were extended to significantly higher doping levels; therefore a more distinct effect of impurity conduction on the electrical properties is expected in respect to lower doped samples.…”

1950°C Post Implantation Annealing of Al+Implanted 4H-SiC: Relevance of the Annealing Time

“…This value is congruent with a transport mechanism through a nearest neighbor hopping between occupied and unoccupied Al acceptor sites. [29][30][31] The formation of an impurity band for every annealing time in the range 5-40 min confirms the high efficiency of the post implantation annealing at 1950…”

Growth of cubic SiC single crystals by the physical vapor transport technique

“…6. The solid dots are measurement points; below 200 K, they are determined by impurity conduction [20]. Above 200 K (see knee-point in the n(1/T)-curve at T ¼ 200 K in Fig.…”