ECE 230B, HW-#3, Winter 2010 1. Consider an n-channel MOSFET with 20 nm thick gate oxide and uniform p-type substrate doping of 10 17 cm-3 . The gate work function is that of n + Si. (a) What is the threshold voltage? Sketch the band diagram at threshold condition, ψ s = 2 B . (b) What is the threshold voltage if a reverse bias of 1 V is applied to the substrate? Sketch the band diagram at threshold. (c) What is the scale length of this device and how short can the channel length be before severe short-channel effect takes place? 2. For an nMOSFET with t ox = 10 nm, μ eff = 500 cm 2 /V-s, v sat = 10 7 cm/s, W = 10 μ m, and L = 1 μ m, assume m = 1. (a) Use the n = 1 velocity saturation model to generate I ds vs. V ds (0-5 V) curves for V g-V t = 1, 2, 3, 4, and 5 V. (Note: I ds = I dsat beyond V dsat ) (b) Now let L vary from 0.5 μ m to 5 μ
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