Academician Zheng Youhui talks about the third generation of semiconductors

Similarly, the development needs of information technology and electronic information technology industries have driven the development of semiconductor materials and technologies.

The third generation of semiconductors refers to wide bandgap semiconductor materials represented by GaN and SiC . They are new wide bandgap semiconductor materials developed in the 1990s after the first generation of semiconductors represented by Ge and Si in the 1950s and the second generation of semiconductors represented by GaAs and InP in the 1970s. They are semiconductor materials with a bandgap width significantly larger than Si (1.12 eV) and GaAs (1.43 eV), and are usually defined as materials with a bandgap width greater than 2 eV .

Currently, there are three types of materials that have attracted much attention: (1) Group III nitride semiconductors, including GaN (3.4 eV), InN (0.7 eV), AlN (6.2 eV) and their solid solution alloy materials; (2) Wide bandgap Group IV compounds , including SiC (2.4~3.1 eV) and diamond film (5.5 eV) materials; (3) Wide bandgap oxide semiconductors , including Zn-based oxide semiconductors (2.8~4.0 eV) such as ZnO, ZnMgO, ZnCdO materials and gallium oxide (β-Ga2O3 , _{4.9 eV} ). Among them, GaN and SiC materials have been successfully applied in many industrial fields.

In the field of optoelectronics , based on the excellent optoelectronic properties of the direct energy gap of all components of GaN, InN, AlN and their solid solution alloys, high-efficiency solid-state light sources and solid-state ultraviolet detection devices have been developed , filling the gap in short-wavelength semiconductor optoelectronic technology and opening a new era of white light lighting, transcendent lighting, full-color LED display and solid-state ultraviolet detection. After nearly 20 years of development, the technology has become increasingly mature, the industry has flourished, and huge scientific, economic and social benefits have been achieved . The market size reached 638.8 billion yuan in 2019.

In the electronics field , based on the superior electronic properties of GaN and SiC, such as wide bandgap, high electron saturation velocity, high breakdown electric field, high thermal conductivity and low dielectric constant, a new generation of microwave RF devices (GaN) and power electronic devices (SiC, GaN) with high energy efficiency, low power consumption, high extreme performance and resistance to harsh environments have been developed.

GaN RF devices Compared with GaAs, they have higher operating voltage, higher power, higher efficiency, higher power density, higher operating temperature and better radiation resistance.

Power electronic devices Compared with Si, it has higher operating voltage, high power density, high operating frequency, low on-state resistance, extremely low reverse leakage current, and high temperature and radiation resistance.

Driven by the demand for new infrastructure in the 5G era , the third-generation semiconductor industry has ushered in a new round of development opportunities characterized by the third-generation semiconductor electronic technology industry, following the development opportunities characterized by the LED semiconductor lighting industry in the early 21st century in response to the world's energy and environmental development strategy needs .

The third-generation semiconductor electronic technology, with its irreplaceable advantages of high energy efficiency , low power consumption , high extreme performance and resistance to harsh environments, plays an important supporting role in the development of 5G information technology and the implementation of new infrastructure from the technical bottom in the two fields of microwave radio frequency and power electronics.

RF devices are the core basic devices of RF technology, and have broad application prospects as RF power amplifiers , active RF switches and RF power sources .

Compared with traditional silicon lateral diffused metal oxide semiconductor (Si-LDMOS) and GaAs devices, GaN RF devices have the advantages of higher operating voltage, higher power, higher efficiency, higher power density, higher operating temperature and better radiation resistance. They support the implementation of new infrastructure, from high-end radar, electronic countermeasures, navigation and space communications and other military electronic equipment applications to 5G base stations, Internet of Things, LiDAR, driverless car millimeter wave radar, artificial intelligence and general solid-state RF power sources and other broad civilian fields, opening up a huge consumer electronics market, and are expected to reshape the new pattern of development in the field of RF technology .

For example, GaN RF devices, as core devices of 5G base station RF power amplifiers (PA), solve the huge energy consumption bottleneck faced by base station communication systems , triggering explosive growth in demand for GaN RF devices.

5G macro base stations operate in high frequency bands, with large losses and short transmission distances. To achieve the same coverage target of 4G signals, 5G base stations will require 3 to 4 times the number of 4G base stations (China currently has 4.45 million 4G base stations). 5G base stations use massive array antenna technology (MIMO) to increase network capacity. The 64-channel MIMO array antenna requires nearly 200 PAs for a single base station, so the power consumption of 5G base stations is 3 to 4 times that of 4G, and the overall energy consumption of 5G base stations will be more than 9 times that of 4G .

Therefore, GaN RF devices have become the inevitable choice for 5G base station PAs due to their irreplaceable advantages, and are also the mainstream direction for 4G base station PA upgrades; the implementation of new infrastructure has opened up a wide range of civilian application scenarios for GaN RF devices in the radar field .

GaN millimeter-wave radar has the characteristics of small size, light weight, high resolution, strong ability to penetrate smoke, fog, and dust, and long transmission distance. It will be widely used in many fields such as Internet of Vehicles, Internet of Things, smart manufacturing, and smart society. For example, GaN millimeter-wave radar in the 77 GHz frequency band is used as a long-range detector for self-driving cars to accurately sense surrounding obstacles to achieve automatic emergency braking, adaptive cruise control, forward collision warning and other active safety functions .

Modern electronic systems or equipment have an increasing demand for power electronic devices, which require not only higher power density and higher energy efficiency , but also high extreme characteristics and resistance to harsh environments . Traditional Si power electronic devices have low conversion efficiency and require huge energy consumption. In addition, the improvement of device performance such as blocking voltage, switching frequency, conversion efficiency and reliability is gradually approaching the physical limit of Si materials, facing severe challenges.

SiC and GaN power electronic devices have superior properties that surpass Si devices. They can meet the new demands of 5G information technology new infrastructure, solve the huge energy consumption bottleneck faced by information infrastructure such as data centers and wireless base stations, and support IT mobile smart terminals to achieve miniaturization, lightweight, and improve endurance , supporting the urgent needs of new energy vehicles, smart energy, rail transit, smart manufacturing and other new infrastructure advantage application fields .

SiC and GaN power electronic devices are suitable for different power application scenarios due to their differences in material electrical properties : SiC power devices are used in high-voltage, high-power power management and control, such as new energy vehicles and their charging infrastructure, new energy power inverters, and smart energy systems.

According to test data, the inverter of new energy vehicles using SiC power modules can reduce switching losses by 75% (chip temperature 215°C), reduce inverter size by 43%, reduce weight by 6 kg, and increase the continuous driving distance of the vehicle by 20%~30% .

China is the world's largest new energy vehicle market. In 2019, China's new energy vehicle sales reached 1.16 million, accounting for 54% of the world's total. The automotive power device market has a huge growth rate, which brings huge development space for the SiC power electronic device and module industry . GaN power devices are used in low-voltage and high-frequency power control, and have extremely broad application prospects in the field of consumer electronics.

In particular, based on its excellent performance of high operating frequency, low dynamic loss, low on-resistance, high temperature resistance and low heat generation, it is very suitable for use as a switching power supply to provide green and efficient power supply for various modern consumer electronic terminals .

For example, as a power adapter fast charging power source, it solves the contradiction of increasing power and increasing volume faced by Si devices in realizing fast charging, and reduces power loss and size by 50% . It can not only shorten the charging time of mobile phones and effectively improve battery life, but also is expected to realize the integration of charging for various mobile terminals such as mobile phones, tablets, game consoles, AR glasses, VR helmets, etc. , support the development of portable IT terminal products, and become the outlet for the development of the current GaN power electronics industry. It is estimated that by 2025, the global GaN fast charging product market will reach more than 60 billion yuan.

Compared with SiC, GaN power devices have faster switching speed, lower on-state resistance, smaller driving loss, higher conversion efficiency, lower heat generation, and Si-based GaN devices have the advantage of lower cost. Therefore, GaN power electronics technology has extremely broad application prospects not only in the large-scale consumer electronics field , but also in various medium and low voltage application scenarios of new infrastructure.

In the era of 5G information technology, the third-generation semiconductors have ushered in new development opportunities. The implementation of new infrastructure has helped the development of the third-generation semiconductor industry enter a golden window period, showing a good momentum of development. It is expected to gradually realize an independent, controllable, safe and reliable third-generation semiconductor industry system, which will complement the advantages of the first and second generation semiconductors and synergistically support the innovative development of new-generation information technology and the high-quality development of China's social economy in the new era.