## Description

5.1 An abrupt silicon pn junction at zero bias has dopant concentrations of Na = 1017 cm-3

and

Nd = 5*1015 cm-3

. T = 300 K.

(a) Calculate the Fermi level on each side of the junction with respect to the intrinsic Fermi

level.

(b) Sketch the equilibrium energy-band diagram for the junction and determine Vbi from the

diagram and the results of part (a).

(c) Calculate Vbi using Equation (7.10), and compare the results to part (b).

(d) Determine xn, xp, and the peak electric field for this junction

5.2 A silicon pn junction in thermal equilibrium at T =300 K is doped such that

EF – EFi = 0.365 eV in the n region and EFi – EF = 0.330 eV in the p region.

(a) Sketch the energy-band diagram for the pn junction.

(b) Find the impurity doping concentration in each region.

(c) Determine Vbi.

5.3 (a) Consider a uniformly doped silicon pn junction at T = 300 K. At zero bias, 25 percent

of the total space charge region is in the n-region. The built-in potential barrier is Vbi = 0.710 V.

Determine (i) Na, (ii) Nd, (iii) xn, (iv) xp, and (v) Emax.

5.4 An “isotype” step junction is one in which the same impurity type doping changes from one

concentration value to another value. An n-n isotype doping profile is shown in Figure 1. (a)

Sketch the thermal equilibrium energy-band diagram of the isotype junction. (b) Using the

energy-band diagram, determine the built-in potential barrier. (c) Discuss the charge

distribution through the junction

Figure 1

5.5 An abrupt silicon pn junction at T = 300 K has impurity doping concentrations of

Na = 5*1016 cm-3

and Nd = 1015 cm-3

. Calculate (a) Vbi, (b) W at (i) VR = 0 and (ii) VR = 5 V, and

(c) |Emax| at (i) VR = 0 and (ii) VR = 5V.

5.6 An ideal one-sided silicon p+n junction at T = 300 K is uniformly doped on both sides of

the metallurgical junction. It is found that the doping relation is Na = 80Nd and the built-in

potential barrier is Vbi = 0.740 V. A reverse-biased voltage of VR = 10 V is applied. Determine

(a) Na, Nd , (b) xp, xn, (c) |Emax|, and (d)Cj

’

.

5.7 Consider a silicon pn junction with the doping profile shown in Figure 2. T = 300 K. (a)

Calculate the applied reverse-biased voltage required so that the space charge region extends

entirely through the p region. (b) Determine the space charge width into the n+

region with the

reverse-biased voltage calculated in part (a). (c) Calculate the peak electric field for this applied

voltage.(You can ignore the influence of p+

)

Figure 2