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Chapter 10: Q65E (page 470)

Question: When electrons cross from the n-type to the p-type to equalize the Fermi energy on both sides in an unbiased diode they leave the n-type side with an excess of positive charge and give the p-type side an excess of negative. Charge layers oppose one another on either side of the depletion zone, producing. in essence, a capacitor which harbors the so-called built-in electric

field. The crossing of the electrons to equalize the Fermi energy produces the dogleg in the bands of roughly Egap , and the corresponding potential differerence

is Egap /e. The depletion zone in a typical diode is wide, and the band gap is 1.0 eV. How large is the built-in electric field?

Short Answer

Expert verified

Answer

The build in electric field is .

Step by step solution

01

Given data

Electric field is uniform.

02

Concept of electric field

Electric field=Potential differencewidth

03

Determine the built-in electric field

Determine the built-in electric field.

Electric field=Potential differencewidth=Egape×width

Solve further as shown below.

Electric field=1.0eVe×1μm=1.0eVe×10-6m=10-6v/m

The build in electric field is 10-6v/m.

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Most popular questions from this chapter

Upon what definitions do we base the claim that the Ψ2px and Ψ2py states of equations 10−1 are related to x and y just as Ψ2pz is to z.

In section 10.2 , we discussed two-lobed Px.Pyand Pz states and 4 lobed hybrid sp3 states. Another kind of hybrid state that sticks out in just one direction is the sp , formed from a single p state and an s state. Consider an arbitrary combination of the 2s state with the 2pz state. Let us represent this bycosτψ2,0,0+sinτψ2,1,0(The trig factors ensure normalization in carrying out the integral , cross terms integrate to 0.leavingcos2τ∫|ψ2,0,0|2dv+sin2τ∫|ψ2.1.0|2dv. Which is 1.)

(a) Calculate the probability that an electron in such a state would be in the +z-hemisphere.(Note: Here, the cross terms so not integrate to 0 )

(b) What value of𝛕leads to the maximum probability, and what is the corresponding ratio ofψ2,0,0 andψ2,0,0 ?

(C) Using a computer , make a density (Shading) plot of the probability density-density versus r and𝛉- for the𝛕-value found in part (b).

From the diagrams in Figure 7.15and the qualitative behavior of the wave functions they represent, argue that a combination of the2pZ(i.e.,ml=0) and the negative of the 2swould produce a function that sticks out preferentially in the positive Zdirection. This is known as a hybridspstate.

The "floating magnet trick" is shown in Figure 10.50. If the disk on the bottom were a permanent magnet, rather than a superconductor, the trick wouldn't work. The superconductor does produce an external field very similar to that of a permanent magnet. What other characteristic is necessary to explain the effect? (Him: What happens when you hold two ordinary magnets so that they repel, and then you release one of them?)

The diagram shows an idealization of the "floating magnet trick" of Figure 10.50. Before it is cooled, the superconducting disk on the bottom supports the small permanent magnet simply by contact. After cooling, the magnet floats. Make a sketch, showing what newmagnetic fields arse. Where are the currents that produce them?
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