646s05hw10 - a = 6 x 10 15 cm-3 and an oxide thickness of...

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ELEG 646; ELEG 446 - Nanoelectronic Device Principles – Spring 2005 Homework #10 (revision 3) - due noon Friday, 20 May 2005, in 140 Evans Hall 1. Using the surface field estimation, (a) calculate the intrinsic depth x i at a temperature of 4K for n- channel Si MOSFET at the onset of strong inversion, assuming that the bulk Fermi potential φ pB = - 0.3 V (even at 4K in this hypothetical case). (b) Briefly explain your numerical result for x i . Discuss the significance of this number, and if it agree with quantum mechanics. 2. Consider the MOS capacitor (same as problem 5 of Homework 9) of area 1 cm 2 made on n- silicon with N D = 1.5 x 10 14 cm -3 and an Al gate. The SiO 2 layer is 200 nm thick. Assume that now the oxide contains 10 12 mobile ions. Determine the flat-band and the threshold voltages when (a) all the ions are uniformly distributed in the oxide, (b) all the ions are at the Si- SiO 2 interface, and (c) all the ions are at the Al-SiO 2 interface. 3. (a) An Al gate enhancement-type n-channel Si MOSFET has a substrate concentration N
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Unformatted text preview: a = 6 x 10 15 cm-3 and an oxide thickness of 0.1 m. The SiO 2 has 10 10 charges cm-2 . Determine the threshold voltage of the transistor. When the transistor is operated in the linear region with V D = 0.5 V, calculate the gate voltage to obtain a drain current of 2 mA. Assume L = 10 m, n = 500 cm 2 /V-sec, and Z = 100L. Calculate the g m of the device and the cutoff frequency of operation f T . (b) What changes will occur in the characteristics of the MOSFET when the gate metal is replaced by p-polysilicon doped with N a > 10 19 cm-3 operated at the same current in the linear region with V D = 0.5 V? Homework assignments will appear on the web at: http://www.ece.udel.edu/~kolodzey/courses/eleg646s05.html Note: On each homework and report submission, you must please give your name, the due date, assignment number and the course number....
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