How great is the application value of gallium nitride, the representative of the third-generation semiconductors?

With the development of artificial intelligence, high-frequency communications and other fields, the first-generation semiconductors such as germanium (Ge) and silicon (Si) have become very mature and are even gradually approaching physical limits. As a result, people are looking for new opportunities in the semiconductor field. Gallium nitride, as a third-generation semiconductor material, stands out among a number of candidates.

Why does gallium nitride stand out among many semiconductor materials?

Gallium nitride belongs to the III-V group of compounds and has the characteristics of direct bandgap semiconductor materials. According to the type of chemical bond, the gallium nitride crystal structure can be divided into hexagonal wurtzite and cubic zinc blende structures. In compounds, there are mainly two types of chemical bonds: ionic bonds and covalent bonds. The more ionic bonds there are, the easier it is to form a wurtzite structure. Due to the large difference in electronegativity between Ga and N, it is easier to form ionic bonds. Therefore, at room temperature, GaN often presents a hexagonal wurtzite structure, which not only gives it high thermal stability and corrosion resistance, but also makes it highly preferred during the growth process, which is conducive to the formation of a single crystal layer with low defect density.

Compared with the first and second generation semiconductors, GaN is a wide bandgap semiconductor with a bandgap width of 3.4eV, almost three times that of Si. It requires higher energy to excite valence electrons into the conduction band, which means that in optoelectronic devices, gallium nitride can emit and absorb higher energy light. In addition, the bottom of its conduction band is at the Γ point, and the energy difference between it and other energy valleys of the conduction band is large, so it is not easy to produce valley scattering, and a very high strong field drift velocity can be obtained. Therefore, gallium nitride devices can withstand greater electric field strengths, have good thermal stability, and maintain excellent performance in high voltage, high current, high frequency, and high temperature scenarios.

What is the application value of gallium nitride?

Based on the above excellent properties, gallium nitride currently has great application value in the fields of radio frequency electronics, power devices, optoelectronics, sensors, etc.

1. RF applications

Compared with Si and GaAS, gallium nitride devices have obvious advantages in high power, high frequency and broadband applications. They are by far the most ideal microwave power devices in the 100GHz range, so they play an important role in radio frequency (RF) applications. , especially in the fields of wireless communications, radar and electronic warfare. For example, in the field of wireless communications, traditional silicon-based RF power amplifiers have problems such as large power loss and low efficiency in high-frequency and high-power applications. They can no longer meet the requirements of new generation wireless communication technologies such as 5G and 6G. If they are adopted Gallium nitride replaces silicon semiconductors in radio frequency front-end modules and can significantly increase the speed and capacity of wireless communications.

2. Power devices

Electronic power devices are inseparable from the development of semiconductor materials. The performance of electronic devices based on Si materials is gradually approaching its limit, and there is an urgent need for better electronic devices. Gallium nitride transistors, with their good dielectric constant, excellent electron mobility, high critical electric field, and high temperature resistance, are beginning to become a potential substitute for Si power devices. For example, with the maturity of gallium nitride process technology, many companies have applied it to “fast charging” chargers, gradually replacing traditional chargers. It can not only achieve a smaller size and faster charging speed under the same power conditions, but also its energy efficiency conversion rate exceeds 90%, which is much higher than traditional silicon-based chargers. In addition, GaN’s high thermal conductivity helps to quickly dissipate heat inside the charger, reduce operating temperature, and improve equipment stability and service life.

3. Optoelectronics

Since Japan developed the homojunction GaN blue LED in 1991, GaN has become the core material of blue light-emitting diodes in semiconductor lighting today. At present, GaN optoelectronic device products mainly include Mini-LED and Micro-LED. Compared with traditional LEDs, MicroLED chips are smaller in size and have the advantages of self-luminescence, low power consumption, high brightness, ultra-high resolution, high color saturation, and better high-definition display performance. They can be applied to ultra-large-screen high-definition smart TVs, consumer electronic displays, as well as consumer electronic backlight applications such as mobile phones and computers, VR/AR and other fields.

4. Sensors

Sensors can detect peripheral signals and convert them into processable output signals, and are widely used in industry, medicine, aviation and other fields. Gallium nitride is widely used in temperature sensors, infrared sensors and pressure sensors due to its excellent performance.

(1) Temperature sensor:
Compared with other sensors, semiconductor sensors have smaller size, high sensitivity, low power consumption and anti-interference ability, and are more suitable for use in IC integrated circuits. However, due to their material properties, Si-based or SiC-based semiconductor sensors cannot work in high temperature environments, while GaN-based power diode devices can work in high temperature, high pressure and high radiation environments, better meeting the needs of temperature sensors.
(2) Pressure sensor:
NASA uses GaN’s high temperature resistance, corrosion resistance and radiation resistance to manufacture GaN/AlGaN-based pressure sensors for use on spacecraft. Its working principle is: the two-dimensional electron gas (2DEG) effect occurring in the AlGaN/GaN heterostructure is used to design sensors that are electrically sensitive to mechanical strain in the device.
(3) Ultraviolet sensor: The ultraviolet sensor based on gallium nitride material is a photodiode with good ultraviolet selectivity. Its response signal to the ultraviolet band is large, while its response signal to visible light (light wavelength range is 390-750nm) is small. Therefore, it will produce a certain voltage output signal after being irradiated by ultraviolet light, and the output voltage signal is in an increasing relationship with the intensity of ultraviolet light. At present, ultraviolet sensors have been applied in military and medical fields such as early cancer detection.

So
Compared with the first and second generation semiconductor materials, gallium nitride can meet the requirements of the next generation of electronic equipment for power devices with higher power, higher frequency, smaller size and working under more severe conditions (higher temperature), becoming the representative of the third generation semiconductor materials. It is currently widely used in power devices, radio frequency, optoelectronics, sensors and other fields. However, due to the compatibility of the substrate and the thin film lattice, gallium nitride is mainly grown on silicon carbide, but currently silicon carbide wafers cannot exceed the size of 6-inch wafers and are relatively expensive. In order to increase the production capacity of gallium nitride devices, it is necessary to further find production methods with lower costs and higher yields in the future.