Question

1. (a) Calculate the value of ni for gallium arsenide (GaAs) at T = 300 K. The constant B = 3.56 × 1014cm−3K 3/2 and the bandgap voltage Eg = 1.42 eV. [5 marks] (b) In a phosphorus-doped silicon layer with impurity concentration of 1017/cm3 , find the hole and electron concentrations at 27oC and 125oC [5 marks] 2. A young designer, aiming to develop intuition concerning conducting paths within an integrated circuit, examines the end-to-end resistance of a connecting bar 10µm long, 3µm wide, and 1µmthick, made of various materials. The designer considers: (a) intrinsic silicon (b) n-doped silicon with ND = 5 × 1016/cm3 (c) n-doped silicon with ND = 5 × 1018/cm3 (d) p-doped silicon with NA = 5 × 1016/cm3 (e) aluminum with resistivity of 2.8µΩcm Find the resistance in each case. For doped silicon, assume µn = 3µp = 1200cm2/V s. (Recall that R = ρL/A.) [25 marks] 3. Assuming that the diodes in the circuits shown in Figure 1 are ideal, utilize Th´evenin’s theorem to simplify the circuits and thus find the values of the labeled currents and voltages. [25 marks] 4. Sketch the transfer characteristic vo versus vI for the limiter circuits shown in Figure 2. All diodes begin conducting at a forward voltage drop of 0.5 V and have voltage drops of 0.7 V when conducting a current iD ≥ 1mA. What type of circuits are these [20 ma