Academician Zheng Youji: the third generation semiconductor ushers in new development opportunities

Zheng Youji, physics expert of semiconductor materials and devices, academician of Chinese Academy of Sciences. He has been engaged in the physical research of semiconductor heterostructure materials and devices for a long time. In recent years, he has mainly devoted himself to the research of the third generation semiconductor materials and devices.

Semiconductor materials are the core basic materials of information technology. One generation of materials, one generation of technology and one generation of industry have supported the earth shaking changes of information technology from the basic technology level for more than half a century and promoted the sustainable and vigorous development of electronic information technology industry.

Similarly, the development demand of information technology and electronic information technology industry drives the development of semiconductor materials and technology.

The third generation semiconductor materials and their applications

The third generation semiconductor refers to the wide band gap semiconductor material represented by Gan and SiC. It is a new type of wide band gap semiconductor material developed in the 1990s after the first generation semiconductor represented by GE and Si in the 1950s and the second generation semiconductor represented by GaAs and InP in the 1970s. That is, the semiconductor material whose band gap width is significantly greater than that of Si (1.12 EV) and GaAs (1.43 EV) is generally defined as the material whose band gap width is greater than 2 ev.

At present, there are three kinds of materials that have attracted much attention: (1) group III nitride semiconductors include Gan (3.4 EV), Inn (0.7 EV), AlN (6.2 EV) and their solid solution alloy materials; (2) SiC (2.4-3.1 EV) and diamond thin film (5.5 EV) materials of wide band gap group IV compounds; (3) Wide band gap oxide semiconductors include ZnO, ZnMgO, zncdo materials and gallium oxide of Zn based oxide semiconductors (2.8-4.0 EV)（ β- Ga2O3，4.9 eV）。 Among them, Gan and SiC materials have been successfully applied in many industrial fields.

In the optoelectronic field, based on the excellent optoelectronic characteristics of Gan, inn, AlN and their solid solution alloys with all component direct energy gaps, high-efficiency solid-state light-emitting 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 illumination, beyond illumination, full-color LED display and solid-state ultraviolet detection. After nearly 20 years of development, the technology has become increasingly mature and the industry has flourished, It has achieved great scientific, economic and social benefits. In 2019, the market scale reached 638.8 billion yuan.

In the electronic field, based on the wide band gap, high electron saturation speed, high breakdown electric field, high thermal conductivity and low dielectric constant of GaN and SiC, 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 environment have been developed.

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

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

New opportunities in the new infrastructure Era

At present, China is making efforts to implement a new generation of information technologies such as 5g communication, Internet of things, big data, cloud computing and artificial intelligence, as well as the construction of new infrastructure (new infrastructure) with the transformation and upgrading of vertical industries such as motor vehicle networking, industrial networking, intelligent manufacturing, smart energy, smart city, medical health and rail transit, to promote China's economic and social innovation and high-quality development.

Driven by the demand for new infrastructure in the 5g era, the third generation semiconductor ushered in a new round of development opportunities characterized by the LED semiconductor lighting industry after meeting the strategic needs of the world energy and environment development in the early 21st century.

The third generation semiconductor electronic technology, with its irreplaceable advantages of high energy efficiency, low power consumption, high extreme performance and poor environment resistance, plays an important supporting role in the development of 5g information technology and the implementation of new infrastructure in the fields of microwave, radio frequency and power electronics.

Microwave RF field

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

Compared with the traditional silicon lateral diffusion metal oxide semiconductor (Si LDMOS) and GaAs devices, Gan RF devices have the advantages of higher working voltage, higher power, higher efficiency, higher power density, higher working 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 vehicle millimeter wave radar, artificial intelligence, general solid-state RF power source and other broad civil fields have opened up a huge consumer electronics market, which is expected to reshape the new pattern of RF technology development.

For example, as the core device of 5g base station RF power amplifier (PA), Gan RF devices solve the huge energy consumption bottleneck faced by the communication system of the base station and cause the explosive growth of the demand for GaN RF devices.

The 5g macro base station operates in the high frequency band, with large loss and short transmission distance. To achieve the same coverage target of 4G signals, the 5g base station will need 3-4 times the number of 4G base stations (currently 4.45 million 4G base stations in China). The 5g base station adopts large-scale array antenna technology (MIMO) to improve the network capacity. The single base station PA demand of 64 channel MIMO array antenna is close to 200, so the power consumption of the 5g base station is 3-4 times that of 4G, The overall energy consumption of a 5g base station will be more than 9 times that of a 4G base station.

Therefore, Gan RF devices have become the inevitable choice of 5g base station PA due to their irreplaceable advantages, and also the mainstream direction of 4G base station PA upgrading; The implementation of the new infrastructure has opened up a broad civil application scene for GaN RF devices in the radar field.

The millimeter wave radar of GaN has the characteristics of small volume, 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 the Internet of vehicles, the Internet of things, intelligent manufacturing, and intelligent society. For example, the 77 GHz band Gan millimeter wave radar is used as a remote detector of autonomous vehicle to accurately sense the surrounding obstacles to achieve automatic emergency braking, adaptive cruise Forward collision warning and other active safety functions.

Power electronics

Power electronic devices are the core devices for power conversion and management. The energy efficiency of devices determines the energy consumption, volume and quality, cost and reliability of electronic systems, equipment and products, and the endurance of intelligent mobile terminals.

Modern electronic systems or equipment have increasingly high demand for power electronic devices, which not only require higher power density and higher