# HW7_2009 - ECE 440 Homework VII Due Friday Fall 2009 1...

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ECE 440 Homework VII Fall 2009 Due: Friday, Oct 23, 2009 1. Field-effect transistors control the output current by changing the charge density in the active region. The following problem is designed to illustrate the effect of changing charge density on the output current. Assume that a rectangular bar of silicon shown below consists of two layers, each of thickness t 1 and t 2 , respectively. The dimensions are D=100μm, W=4μm, t 2 =5μm and t 1 =100Å. The t 1 layer is uniformly doped with N d1 /cm 3 donors and N d2 =10 14 /cm 3 donors are also uniformly doped in the t 2 layer. A bias of 1 V is applied between x=0 and x=W. Determine the output current, I d , for different carrier densities in the t 1 layer. Specify the current for N d1 =10 17 /cm 3 , 1.1x10 17 /cm 3 , 10 18 /cm 3 , and 1.01x10 18 /cm 3 . Also, estimate the “Amplification Factor” of this device for N d1 =10 17 /cm 3 and N d1 =10 18 /cm 3 . The “Amplification Factor” is defined as AF= (1/qt 1 )( I d / N

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HW7_2009 - ECE 440 Homework VII Due Friday Fall 2009 1...

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