A semiconductor device is an electronic device that uses the special electrical properties of semiconductor materials to perform specific functions between good electrical conductors and insulators, and can be used to generate, control, receive, transform, amplify signals, and perform energy conversion.
The semiconductor material of the semiconductor device is silicon, germanium or gallium arsenide, which can be used as a rectifier, oscillator, light emitter, amplifier, light meter and other equipment. To distinguish it from an integrated circuit, it is sometimes referred to as a discrete device. The basic structure of most two-terminal devices (I. e., crystal diodes) is a PN junction.
Semiconductor devices (semiconductor devices) usually use different semiconductor materials, using different processes and geometric structures, and have developed a wide variety of crystal diodes with different functional uses. The frequency coverage of crystal diodes can range from low frequency, high frequency, Microwave, millimeter wave, infrared until light wave. Three-terminal devices are generally active devices, typically represented by various transistors (also known as transistors). Transistors can be divided into two types: bipolar transistors and field effect transistors. According to different uses, transistors can be divided into power transistors microwave transistors and low-noise transistors. In addition to general transistors for amplification, oscillation, and switching, there are also some special-purpose transistors, such as phototransistors, magneto-sensitive transistors, field effect sensors, etc. These devices can not only convert the information of some environmental factors into electrical signals, but also have the amplification effect of general transistors to obtain a larger output signal. In addition, there are some special devices, such as single junction transistors can be used to generate sawtooth waves, thyristors can be used for a variety of high-current control circuits, charge coupled devices can be used as a camera or information storage devices. In military equipment such as communications and radars, weak signals are received mainly by high-sensitivity, low-noise semiconductor receiving devices. With the rapid development of microwave communication technology, microwave semiconductor low-noise devices are developing rapidly, the working frequency is increasing, and the noise figure is decreasing. Microwave semiconductor devices have been widely used in air defense and electronic warfare systems due to their excellent performance, small size, light weight and low power consumption.