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4. N. Newman, MSE494/598 Handout #8 page 4 Potential diagram of Schottky barrier (n-type material) Metal Semiconductor CBM VBM bb Fermi-level

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16. N. Newman, MSE494/598 Handout #8 page 16 Electrostatics of p++ / n junction or n-Schottky barrier d 2 V/dx 2 = -  /  q N d  + + + + + + +  E = dV/dx = -  /  dx = - q N d x  V = - q N d x  dx = - q N d x 2 / 2  x=0 -qN d x d /  E x=x d -V

17. N. Newman, MSE494/598 Handout #8 page 17 Transition Capacitance of p++ / n junction or n-Schottky barrier V d - V applied = - q N d x d 2 / 2  i.e. x d = (V applied -V d ) 2  / q N d PARALLEL PLATE CAPACITOR C =  A / x d C T = A [q N d  / 2 (V applied - V d )] 1/2

18. N. Newman, MSE494/598 Handout #8 page 18 1/C T 2 = 2 (V applied - V d ) / (q N d  A 2 ) 1/C T 2 V applied Slope o 1/N d c VdVd

19. N. Newman, MSE494/598 Handout #8 page 19 N d 1 N d 2 V applied 1/C T 2 Slope o 1/N d 1 c VdVd Slope o 1/N d 2 c N d 2 >> N d 1 Can tailor C(V) by the control of the doping profile, for example for a hyperabrupt junction C is proportional to V -2 facilitating  = (LC)- 1/2 being proportional to a control voltage 1/C T 2 = 2 (V applied - V d ) / (q N d  A 2 )

20. N. Newman, MSE494/598 Handout #8 page 20 Diffusion Capacitance of p++ / n junction In forward bias, holes are injected into the n-type region. Q D = A q p no L p (e v D /V T - 1) = (L p 2 /D p ) I =  I C D = dQ/dV =  dI / dV =  I / (n V t )

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29. N. Newman, MSE494/598 Handout #8 page 29 NPN Bipolar Junction Transistor (BJT)

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