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4. RESISTANCE UNDER DOPING A Si bar has a length of 10 mm and a cross-sectional area of 1 mm*. At T = 300K, nj; = 1.5 x 10'cm \"3. Mobility values can be read from the attached figure. Calculate its resistance if it is: (A) Without any doping. (B) Doped with 5 x 10!'cm~? phosphorous. (C) Doped with 5 x 10!'cm~? phosphorous and 2 x 10'cm~? boron. 1600 - 1400 1200 LOOO 800 F 600 Mobility (cm7/V-s) 400 200 0 : 10'4 10' 10' 10" 10' 10" 10 N, + Ng (ions/em*) FIGURE 2-5 The electron and hole mobilities of silicon at 300 K. At low dopant concentration, the electron mobility is dominated by phonon scattering; at high dopant concentration, it is dominated by impurity ion scattering