16. Fill in the gaps.

1. In the N-type region electrons are in … and in the P-type region holes … .

2. Since the N-type region loses … and gains … and the P-type region loses … and gains …, the region to the left of the junction becomes … and the region to the right of the junction becomes … .

3. If a silicon crystal is doped with … at one end and with … at the other end, the crystal will have both … and there will be … between them.

4. In both regions the probability of a minority charge carrier meeting and recombining with a majority charge carrier is … and the minority charge carrier lifetime is … .

5. The movement of holes and electrons across the junction … current and this is known as … .

17. Read the text “The p-n Junction“ again in your memory and answer the questions.

1. What is a sign of charge carriers in the N-type and P-type regions?

2. What regions include majority charge carriers and minority charge carriers?

3. What is their lifetime?

4. On average more electrons cross the junction from right to left than from left to right, don’t they?

5. How can you define the process of diffusion?

6. Do you know what the diffusion current is?

7. What will happen if a hole passes into the N-type region or an electron passes into the P-type region?

Speaking

18. Summarize the text “The P-N Junction” in 150 words.

19. Draw a picture of a P-N junction and describe it.

Start your description like this: “This plane AB is the P-N junction.”

20. Act as an interpreter. Translate the description of the P-N junction given by your group mate from English into Russian.

21. Divide into two groups. Group A translates text A “The P-N Junction”, group B translates text B “Joining P- and N-Type Germanium” with a dictionary in writing.

Text A

The P-N Junction

If the crystal was neutral before diffusion took place, it must be neutral afterwards. Further, because both regions were also originally neutral they must contain equal and opposite charges after diffusion. These charges have an attractive electric force between them and are not able to diffuse away from the vicinity of the junction . The two charges are concentrated immediately adjacent to the junction, and produce a potential barrier across the junction.

The polarity of the potential barrier is such as to oppose the further diffusion of majority charge carriers across the junction, but to aid the movement of minority charge carriers; this gives rise to a minority charge carrier current in the opposite direction to the diffusion current.

The difference in potential from one side of the junction to the other is called the height of the potential barrier and is measured in volts. The height of the potential barrier attains such a value that the majority charge carrier (diffusion) currents and minority charge carrier current are equal and so the net current across the junction is zero. Any charge carriers entering the region on either side of the junction over which the barrier potential is effective are rapidly swept out of it, and hence this region is depleted of charge carriers.