SEMICONDUCTOR DEVICE PHYSICS AND DESIGN

348 CHAPTER 7. TEMPORAL RESPONSE OF DIODES AND BIPOLAR TRANSISTORS

–10 –8 –6 –4 – 2

4

8

12

16

20

nfully depleted-region 24

}

Nd

p+ n n+

Na

W

(F

–2

)x

10

23

V (V)

(^12) C
0 1.0
V = 0.68 V
Figure 7.23: Plot ofC^12 vs.Vfor problem 7.1.
can be exploited for high-performance HBTs. InGaAs has extremely attractive electronic prop-
erties and is therefore the material of choice for all high-speed/high-frequency applications. The
InGaAs/InP HBTs have achievedfτvalues of over 600 GHz.

7.7 PROBLEMS ....................................

• Section 7.2

Problem 7.1TheC^12 versus applied voltage relation in a siliconp+−n−n+junction

diode is measured to have a form shown in figure 7.23. Calculate the thickness of the

n-region, the built-in voltage, and theNaandNdconcentrations in thep+andnregions.

The diode area is 10 −^3 cm^2. Also calculate the width of then-region.

Problem 7.2Consider a long basep+ndiode that is biased to carry a forward current of

1 mA. The junction capacitance is 100 pF. If the minority carrier lifetimeτpis 1 μs, what is

the admittance of the diode at 300 K for a 1 MHz signal?

Problem 7.3Ap+-nsilicon diode has an area of 10 −^2 cm^2. The measured junction

capacitance is given by (at 300 K)

1

C^2

=5× 108 (2. 5 −4V)