Semiconductors are a technology product closely related to our daily lives. From the simplest electric lights, to mobile phones, laptops, to a country's aerospace industry, all are based on semiconductor technology. It can be said that without semiconductors, our current lives would be completely different. However, although semiconductor technology is so important, not many people truly understand it. Therefore, as an elective course paper, I would like to briefly discuss my understanding of semiconductor technology here, which can be considered as the experience of taking this course.
Firstly, it is necessary to have a clear definition of semiconductors, as quoted 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's a bit broad. Regarding my understanding, semiconductors are a type of material with special electrical properties that can be used to make a special class of electronic components, including diodes, transistors, integrated circuits, etc. In the following section, I am going to provide a brief description of a fundamental characteristic of semiconductors, the P-N junction.
There are no natural semiconductors in nature, and the so-called semiconductors are the result of human changes in nature, which is enough to demonstrate the greatness of humanity. Semiconductor materials can generally be divided into two types based on their conductive properties, P-type semiconductors and N-type semiconductors. If we add a small amount of arsenic or phosphorus to pure silicon, there will be an additional free electron, forming an N-type semiconductor. If we add a small amount of boron to pure silicon, we will actually lose one electron and form a hole, forming a P-type semiconductor.
If the material of a semiconductor suddenly changes from a p-type semiconductor to an n-type semiconductor in a single crystal structure, this is called a P-N junction. In the P-region, holes constitute the dominant carriers, hence they are called majority carriers. A small portion of the electrons generated by heat 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 area is called the Depletion region. It acts like an insulator.
One of the most important characteristics of P-N junctions is unidirectional conductivity. When a forward voltage is applied to the P-N junction, most of the charged carriers pass through the P-N junction, resulting in a large current flowing through it. However, when a secondary voltage is applied, the charged carriers generated by impurities move in the opposite direction of the junction, with only a small leakage current flowing through. As the reverse voltage increases, the leakage current remains small until a critical voltage is reached. After this point, the current suddenly increases, indicating that the junction has been broken down. Although other types of junctions have been invented, including P-N-P, N-P-N, etc., P-N junctions are still considered the most basic type of semiconductor devices.
Since the invention of semiconductors by humans, human society has undergone unprecedented changes. So how did semiconductors grow?
As early as the 19th century, people had already begun to pay attention to it. In 1874, Braun of Germany noticed that the conductivity of sulfides was 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 exists an energy barrier between metals and semiconductors, and his main contribution lies in calculating the shape and width of this energy barrier. In the field of semiconductors, energy band theory is equally important as rectification theory, and Bloch has made significant contributions in this regard.
After World War II, Bell Labs of the United States decided to carry out a plan on semiconductors, but many experiments failed. Until December 16, 1947, Braden used a triangular plastic, and Shenzhen Diode stuck gold foil on the plastic foot, and then cut a slit with a blade to form two electrodes close to each other, forming a point contact transistor. In this way, the first artificial semiconductor was born.
The initially designed semiconductor cannot be put into large-scale production. It was not until 1960 that Bell Labs developed the epitaxial technology, and the semiconductor industry gained the ability of mass production, finally stood firm and began to grow rapidly.
In 1952, the British man Dumo began to propose the concept of integrated circuits. Until 1963, the first integrated circuit product was launched into the market, a total of ten years. Since then, the number of components on integrated circuits has doubled every year, which is known as Moore's law. Until today, a Very Large Scale Integration can contain tens of millions of components!
However, the development of semiconductors in China still has a long way to go. Experts analyze that the overall level of semiconductor technology development in China is still in its infancy, and the industrial chain is not matched and incomplete. For example, the development level of manufacturing and design, packaging and testing industries is imbalanced, and the scale is mutually imbalanced, among other prominent contradictions; The technical level is low, the design industry is small-scale, the output value is small, and packaging testing is still at a low level; Poor research and development capabilities, lack of independent intellectual property rights, and so on. The solution to these problems with SMD diodes requires the efforts of knowledgeable individuals in our generation.
Two promising products regarding semiconductors now are semiconductor lamps and solar energy technology. Here is a brief description of semiconductor lights, also known as LED lights.
Nowadays, global environmental awareness is rising, and LED lighting has become one of the main development policies in many countries. The current development plan set by the United States is that LED lighting will completely replace incandescent lamps in 2012, while the European Union will restrict the sale of 100 watt incandescent lamps from 2009 and will completely ban them by 2012 at the latest.
So, why do LED lights have such great charm? It is a solid-state semiconductor device that can directly convert electricity into light. The heart of an LED is a semiconductor chip, which consumes only 1/10 of the power of an ordinary incandescent lamp at the same brightness, but its lifespan can be extended by 50 times. In addition, LED, as a light source for indoor lighting fixtures, also has many advantages such as energy saving, environmental protection, vibration resistance, small size, low attenuation, suitability for low-temperature environments, and high luminous efficiency.
However, if semiconductor lamps are to completely replace incandescent and energy-saving lamps, Schottky diodes must achieve LED bulb luminous flux of 1000 Lm, and the cost of LEDs must be reduced to $1 per thousand lumens in order to be fully popularized. This is actually considering the production cost issue, and secondly, the heat dissipation issue is the bottleneck that affects the popularization of high-power LEDs.
So what are the future development trends of the semiconductor industry? Professionals analyze that in order to meet the rapidly growing demand in High-voltage direct current, high-voltage reactive power compensation, high-voltage motor control and other fields, high-power semiconductor devices are developing in the direction of high current and high voltage, and the modern high-power semiconductor technology of fast recovery diodes is also showing the trend of integration, high-frequency, intelligence and digitalization.
Conclusion: In the past 60 years since its birth, semiconductor technology has made significant progress. 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!