Semiconductor is a technical product that is closely related to our lives. From the simplest electric light, to mobile phones, laptops, to the aerospace industry of a country, all of them are based on semiconductor technology. It can be said that if there is no semiconductor , our current human life will be completely different. However, although semiconductor technology is so important, there are not many people who really understand it. Therefore, as a thesis of an elective course, I would like to briefly talk about my understanding of semiconductor technology here, which can be regarded as the experience of taking this course.

First of all, there must be a clear definition of semiconductors. Here is the definition in the Encyclopedia Britannica: any of

A class of crystalline solids intermediate in electrical conductivity between a conductor and an insulator.

Although this is the definition of an encyclopedia, I think it is a bit broad. As far as my understanding is concerned, semiconductors are a class of materials with special electrical properties that can be used to make a class of special electronic components, including diodes, transistors, integrated circuits, etc. In the following part, I am going to give a brief description of a basic characteristic of semiconductors, the P-N junction.

Natural semiconductors do not exist in nature. The so-called semiconductors are the result of human beings changing nature, which is enough to see the greatness of human beings. Semiconductor materials can generally be divided into two types according to their conductivity properties, P-type semiconductors and N-type semiconductors. If we dope a little arsenic or phosphorus in pure silicon, there will be one more free electron, thus forming an N-type semiconductor. If we dope a little boron in pure silicon, one electron will be lost instead, and a holes, thus forming a P-type semiconductor.

If in a single crystal structure, the semiconductor material suddenly changes from a p-type semiconductor to an n-type semiconductor at a certain place, this is called a P-N junction. In the P region, holes constitute the dominant carriers, so they are called majority carriers. A small fraction of thermally generated electrons will still exist in the p region. In the n region, electrons are the majority carriers. Near the pn junction, there are no charged carriers. This region is called the depletion layer, which behaves like an insulator.

One of the most important characteristics about P-N junction is exactly unidirectional conductivity. When a forward voltage is applied to the P-N junction, most of the charged carriers pass through the P-N junction, so a large current flows through it. However, when a secondary voltage is added, the charged carriers generated by the impurities go in the opposite direction of the junction, and only a small leakage current flows. When the reverse voltage increases, the leakage current remains small until a A critical voltage is reached, after which point the current will suddenly increase, indicating that the junction has broken down. Although other types of junctions have been invented, including P-N-P, N-P-N, etc., the P-N junction is still considered the most basic type of semiconductor device.

Since semiconductors were invented by humans, human society has undergone unprecedented changes, so how did semiconductors grow for a long time?

As early as the 19th century, people have begun to pay attention to it. In 1874, Braun in Germany noticed that the conductivity of sulfide is related to the applied voltage, which is the rectification effect of semiconductors. In terms of rectification, Schottky of Germany published an important paper on rectification theory in 1939. In the German Journal of Physics, he believed that there is an energy barrier between metals and semiconductors. His main contribution lies in Calculate the shape and width of this energy barrier. In the field of semiconductors, energy band theory is as important as rectification theory, and Bloch has made great contributions in this regard.

After World War II, Bell Laboratories in the United States decided to carry out a semiconductor project, but many experiments failed until December 16, 1947. Braden used a triangular piece of plastic, and Shenzhen diodes were pasted on the plastic feet. The gold foil, then cut a thin slit with a blade to form two closely spaced electrodes that make up a point-contact transistor. In this way, the first man-made semiconductor was born.

However, the originally designed semiconductor cannot be mass-produced. It wasn’t until 1960 that Bell Labs developed epitaxial technology, and the semiconductor industry gained the ability to produce in batches. It finally gained a foothold and began to grow rapidly.

In 1952, the British Dumo began to propose the idea of integrated circuits. Until, in 1963, the first integrated circuit product was put on the market, a total of ten years. But since then, the number of components on integrated circuits has doubled every year, which is the famous Moore’s Law. Until today, a very large scale integrated circuit can contain tens of millions of components!

However, the development of semiconductors in my country still has a long way to go. Experts analyze that the overall level of my country’s semiconductor technology development is still in its infancy, and the industrial chain is not complete and perfect, such as the unbalanced development level of the manufacturing and design, packaging and testing industries, and the unbalanced scale of each other. Small, small output value, low level of packaging and testing; poor research and development capabilities, lack of independent intellectual property rights, etc. The solution to these problems requires the hard work of young people of insight in our generation.

Two more promising products about semiconductors are semiconductor lamps and solar energy technology. Here is a brief description of the semiconductor lamp, that is, the LED lamp.

Nowadays, the global awareness of environmental protection is on the rise, and LED lighting has become one of the main development policies of many countries. According to the current development plan set by the United States, LED lighting will fully replace incandescent lamps in 2012, while the European Union has restricted the sale of 100-watt incandescent lamps since 2009, and will completely ban incandescent lamps in 2012 at the latest.

So why is LED light so attractive? It is a solid-state semiconductor device that can directly convert electricity into light. The heart of the LED is a semiconductor chip. Under the same brightness, its power consumption is only 1/10 of that of ordinary incandescent lamps, but its life can be extended. 50 times. In addition, as the light source of indoor lighting fixtures, LED also has many advantages such as energy saving and environmental protection, vibration resistance, small size, not easy to attenuate, suitable for low temperature environment and high luminous efficiency.

However, if semiconductor lamps are to completely replace incandescent lamps and energy-saving lamps, Schottky diodes must reach the luminous flux of LED bulbs up to 1000Lm, and the cost of LEDs must drop to $1 per thousand lumens before they can be fully popularized. This is actually due to production cost considerations. Secondly, heat dissipation is the bottleneck that affects the popularization of high-power LEDs.

So what is the future development trend of the semiconductor industry? According to the analysis of professionals, in order to meet the rapidly growing demand in the fields of high-voltage direct current transmission, high-voltage reactive power compensation, and high-voltage motor control, high-power semiconductor devices are developing in the direction of high current and high voltage, and modern high-power semiconductor technology of fast recovery diodes has also shown The trend of integration, high frequency, intelligence and digitization.

Conclusion: Semiconductor technology has made considerable progress in the past 60 years since its birth. It not only immerses countless scientists in the charm of semiconductor science, but also makes great contributions to society.

We believe that semiconductor science and technology will always have infinite vitality!