Über Zusammenhänge zwischen Elektronenspinresonanz, elektrischer Leitfähigkeit und Photoleitung bei reinem und dotiertem Bor

Abstract

The conductivity mechanism in pure and doped, β-rhombohedral, polycrystalline boron between 1.5 °K and 900 °K is clarified by measurements of electrical conductivity, photoconductivity, electron paramagnetic resonance and thermoelectric effect. The semiconductor behaviour of boron between 1.5 and 900 °K is similar to that of doped and compensated germanium and silicon at helium temperatures concerning the temperature-independent number of carriers and the thermally activated conduction process at low and high carrier concentrations. The paramagnetic centres are nearly localized electrons at 1.5 °K and nearly free electrons at 900 °K with a continuous transition between these two extreme kinds of behaviour. Mobilities of charge carriers in carbon doped boron over a range from 10¹⁶ cm⁻³ to 10²⁰ cm⁻³ and 77 °K to 900 °K were measured for the first time and were found to obey an exponential law.