N. Newman, MSE494/598 Handout #8 page 1
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N. Newman, MSE494/598 Handout #8 page 4 Potential diagram of Schottky barrier (n-type material) Metal Semiconductor CBM VBM bb Fermi-level
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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
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
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
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 )
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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N. Newman, MSE494/598 Handout #8 page 29 NPN Bipolar Junction Transistor (BJT)
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