Test 1 with Solution - Electronics - Spring 2011 | ECE 2204, Exams of Basic Electronics

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, Bar Gm 754) ECE 2204 (Spring 2011) Sty) Test #1 Question #1 (30 points): A piece of germanium is doped with gallium and arsenic atoms such that [Ga] = 2 x 10" and [As] = 2 x 10" cm”, and it is maintained at a temperature of 100 °C. Is this sample of germanium an n-type or p-type semiconductor? What is the electrical tesistivity of this piece of material? Assume that the relationships between 4, and yz, in germanium at 100 °C and the total impurity concentration are the same as those in silicon at 300 K. State all assumptions. Question #2 (70 points): A one micron thick piece of silicon is doped non-uniformly with donors and is maintained at a temperature of 50 °C. The donor concentration varies linearly from Np = 0 at x= 0 to Np = 2 x 10! om? at x = 1.0 jm. Determine the spatial variation of electron density, a(x), hole density, p(x), and electric field, E(x), throughout the sample thickness. Calculate the diffusion and drift components of both the electron and hole current densities at x = 0.5 jum. State all assumptions, February 1, 2011