Mid Term Exam
July 19, 2002
Calculate the electron and hole concentrations, E f , and the resistivity at room temperature.NA = 3x1017cm-3
ND = 2x1017cm-3NA + ND = 5x1017cm-3
The hope concentration, p = NA - ND = 1017cm-3.
The electron concentration, n = ni2/p = 2x1020/1017 = 2x103 cm-3.
Ef - Ei = -Vt ln [(NA - ND)/ni] = -0.0259 ln [1017/1.5x1010] = -0.407V
Resistivity
Mobility depends on the total doping, NA + ND = 5x1017cm-3. From the table hole mobility is about 300 cm2/V-s.
rho = 1/[qup(NA - ND)] = 1/[1.6x10-19 x 300x1017] = 0.2 ohm-cm
Doping
cm-3Electron
Mobility
(cm2 V-sec)Hole
Mobility
(cm2 V-sec)1014 1500 450 1015 1500 450 1016 1400 440 1017 1200 410 1018 800 200 1019 200 150 1020 90 50