"The classmate in the back, are you in such a hurry to leave?"

Le Yuan looked to the side, made sure that he was talking about himself, and was about to explain, when he heard the old teacher say: "Your current students, it is really not as good as one term, and the professional classes are not good to listen to, and you think about some opportunistic and crooked things all day long, don't think that I don't know what you are sitting here today and want to do." Pen %Fun %Pavilion www.biquge.info"

The whole classroom was still a little fragmented, but when he said this, they were all silent, and they didn't know whether to look at Leyuan or the podium. Many people saw a dark-skinned man in a plaid shirt standing there in the back, and they were a little puzzled: This is not from our class either!

When Leyuan heard this, he also knew that the old teacher understood what the students meant, and deliberately pretended to be confused. However, he happened to be at the meeting, and he was inexplicably lying down, and he really couldn't say it, because the old teacher continued to say: "Seeing that your second school year is almost over, I think most of you have already bought train tickets." But have you ever thought that when you go back, your relatives and friends ask you what you have studied and what you have studied, and what should you say? I am afraid that you will not be able to say any professional knowledge other than the name of your major. ”

"Although our school is not a top school, it is not easy to get into our school. As far as I know, the score line of your major is stuck in more than 20,000 places in the province. In other words, among the more than 300,000 science students, you are all the best, and there are still 280,000 people behind you who do not do well in the exam. ”

After saying this, the old teacher was also a little thirsty, took a sip of the cup, and continued: "What are you going to university for, just so that when you go home, others call you a college student? Then I advise you not to be delusional, now our students in a university may still be of some use, but I believe that in a few years, undergraduates, graduate students, will definitely not be able to count, and it will be useless for you to hold on to an empty shell of a university." ”

Leyuan nodded secretly, since the expansion of enrollment in 1999, the annual college enrollment has increased by 25 percent per year. Although the impact of this expansion has not yet been fully felt in 2006, in another two or three years, people's impression of the word college student will completely change. In the back, even the students who came out of a college were not enough to see at all.

What the old teacher said was very reasonable, but it had nothing to do with Le Yuan's half a dime, he just came over for a walk after he was full, and came in with curiosity to take a look, but he didn't expect to be caught, and set a typical example.

When the old teacher said this, he also sighed, "I'm afraid you haven't learned much of what you have learned this year, so I'll ask, who of you knows, what are the three stages of semiconductor preparation?"

As soon as he asked, a few students raised their hands, but the old teacher ignored them and said to Leyuan: "What about you, do you know?"

For Leyuan, this question is no different from asking him how many times one plus one is equal, and he said with a smile: "I don't know if it is three stages: impurity engineering, defective engineering and energy belt engineering." ”

The old teacher glanced at Le Yuan in some surprise, and then nodded: "It's not bad, then you can sit back in your seat." ”

Leyuan instantly felt that he had beeped a dog, he obviously wanted to go out, but he didn't have the heart to explain to the old teacher, anyway, he wouldn't die if he sat for a while, it was better not to explain, otherwise it was very likely that he couldn't say it clearly.

Seeing Le Yuan sitting back, the old teacher asked again, "Then do any of you know what these three stages are?"

Seeing this situation, the old teacher smiled and encouraged: "It's okay, you can say as much as you can, even if it's wrong." ”

But even though he said this, no one raised his hand, and the old teacher frowned and said, "That classmate just now, you stand up and answer." ”

Leyuan looked at the old man, and almost didn't scold, howoldareme!

But he can only answer honestly, because the question is simpler than explaining where he came from.

He stood up and looked at the people in the front row, both men and women turned their heads to look at him, most of them with curious eyes, and of course a few were gloating.

Leyuan rolled up his sleeves that didn't exist at all, and talked eloquently: "There are many types of devices, and the specific requirements are different, but in general, they can be divided into three stages: impurity engineering, defect engineering, and energy belt engineering. Impurity engineering is the control of impurities in materials to achieve the function of a device. There is a harmful side and a beneficial side to the impurities of semiconductor materials. ”

As soon as he opened his mouth, it was a technical term, and it sounded clear-eyed, except for the old teacher who nodded while listening, everyone else had an unclear face.

"To do this, superpurification is first carried out to improve the overall purity of the material. The required impurities are then incorporated to form the type of conductivity, resistivity, p―n junction, luminous energy level and the center, the ohmic contact between the semiconductor and the metal, etc. Defect engineering is the elimination of defects and the intentional introduction of defects to achieve device functionality.

Defects in semiconductor materials are harmful in most cases, so the focus of semiconductor material preparation is on semiconductor crystal growth, one of the purposes of which is to eliminate crystal defects in the material, including grain boundaries, dislocations, microdefects, etc., and to prevent the introduction of secondary defects during processing. ”

As he spoke, Leyuan remembered the days when he was in school and in the research institute in the past, and he became more energetic.

"An example of the role of utilizing defects is the absorption of 34 divisions on silicon wafers and the preparation of semi-insulating gallium arsenide single crystals using deep energy levels. Band engineering is the fabrication of thin films and devices according to the designed band structure. This includes semiconductor heterojunctions, quantum wells, and semiconductor superlattices, which require materials to be fabricated into microstructures with atomic-level precision. The above control of impurities, defects, and band structure are all part of the intrinsic quality of the material, and the semiconductor material is provided to the device fabrication process in a certain geometry. ”

Speaking of which, Leyuan has basically explained the three stages clearly, but he continued: "In order to meet the above requirements, the preparation process should be divided into: material super-purification, semiconductor crystal growth ......"

The old teacher had been listening to him carefully, and suddenly heard that the preparation process was about to come out, so he hurriedly interrupted: "Okay, okay! ”

And the others were already dumbfounded, looking at Leyuan, their eyes were like seeing aliens. Especially the few people who gloated before, at this time, there were also 10,000 mud horses galloping through their hearts.

Le Yuan smiled slightly: "Are you satisfied?"