Question

As starting material we have 99.999999 at.% Si (= 8 nines or 8N). The only dopant is aluminium and we call this 8N-Si(Al) (see periodic table). At room temperature the electron mobility in Si is µe=0.25 m2/(Vs), the hole mobility µh=0.05 m2/(Vs), unit of charge 1.6 10-19 C, the density of Si ρ=2.33 g/cm3, the atomic mass of Si 28.08 and Avogadro’s number 6.022 1023. a. What is the electrical conductivity of this material at room temperature (where conduction can be considered in the pure extrinsic exhaustion/saturation regime)? Apart from the starting material, also the auxiliary materials 8N-Si(Ga) and 8N-Si(As) are in stock. b. We want to make an intrinsic semiconductor by melting the starting material together with one of the auxiliary materials. Which auxiliary material we have to choose and in what ratio we have to melt the two materials together? c. With which one of the two auxiliary materials together with the starting material can we make a semiconductor with a conductivity (at room temperature) of σ = 8.0 (Ωm)-1? What is then the type of semiconductor we have? What is then the required ratio for melting together the starting material with the auxiliary material?

Answer 1