InP (Indium Phosphide)
It is a non-naturally occurring semiconductor material with excellent electro-optical conversion efficiency, high electron mobility, high temperature resistance and strong radiation resistance.
As the representative of the second-generation semiconductor material, InP has strong application potential in the fields of optoelectronics and microelectronics, and also has great value in military high-performance satellites, missiles, radars and other weapon systems. These characteristics made InP quickly attracted the attention of scientific researchers from all over the world after its first successful growth in the late 1950s, and the R&D team of ZGDZ was also one of them.
On the road of R&D of the whole industry chain of InP single crystal, ZGDZ independently designed and manufactured China's first high pressure single crystal furnace. China's first LEC InP single crystal and the first batch of GaAs single crystals were grown from this high pressure single crystal furnace.
In addition, the ZGDZ R&D team also invented the in-situ synthesis continuous crystal growth equipment and method for InP and GaAs materials. Breakthrough in the low temperature synthesis process of GaAs. At the same time, the exploration results of the ZGDZ R&D team in materials and related technologies have provided key materials for the development of InP devices in China.
The demand for large-sized InP monocrystalline products is increasing day by day. However, due to the difficulty of preparation technology, only a few companies such as Japan's Sumitomo, France's InPact, and the United States' AXT are capable of mass-producing 2-4-inch InP single crystals, while the preparation of 6-inch InP single crystals is limited to reports.
At this time, the InP research group where the ZGDZ R&D team is located has been engaged in related research for nearly 40 years, and the accumulated technical and theoretical achievements have provided it with rich scientific research soil.
The temperature is 1062°C and the pressure is 4MPa, which are the basic conditions required for the growth of InP. Under such high temperature and high pressure conditions, any operation must be cautious, and the resulting design difficulty can be imagined. After repeated demonstrations, supplemented by dozens of innovative design inventions, ZGDZ's R&D team continued to tackle key problems, and finally developed a key equipment with completely independent intellectual property rights in 2012 – a multi-functional large-scale high-pressure single crystal furnace.
This equipment has a large caliber and can perform high-weight and large-capacity synthesis. It grows 6-8-inch InP single crystals by LEC, VB, VGF and other methods. It realizes all design, manufacturing and localization of software, and has thermal stability. high characteristic.
Compared with the single crystal furnaces of the British MR company and the US Air Force Laboratory, ZGDZ's single crystal furnaces have achieved two "increases": larger size and more functions. With this "sharp weapon", the blockade of the core equipment in the high-end InP semiconductor field by developed countries will be broken, and it will also fill the gap in China in this field.
With a large-scale high-pressure single crystal furnace, the next problem to be solved is the thermal field design problem. In view of the characteristics of strong convection and high temperature fluctuations in large-size single crystal furnaces, the R&D team of ZGDZ proposed an adjustable closed thermal field structure.
Based on this invention, at the end of 2013, the team successively produced InP monolithic single crystals with a diameter of 6 inches and a weight of nearly 10kg, which became the heaviest and largest crystal in the world at that time. world leading level. The significance of this achievement is that it not only breaks through the key technologies in the preparation process, but also makes the large-scale industrial application of InP possible.
In the field of polycrystalline synthesis, on the basis of clarifying the physical mechanism of injection synthesis, the team invented a double-tube rapid injection synthesis method. Using this method, 6 kg of InP polycrystalline can be synthesized every 3 hours, and a breakthrough in the synthesis of 20 kg of high-purity InP is achieved. The key core technology has realized the "double improvement" of synthesis efficiency and industrialization level.
In addition, the team also creatively proposed the continuous crystal growth technology of injection synthesis, which can be used for the preparation of ultra-high-purity polycrystals. The purity of ultra-high-purity polycrystals grown by this technology exceeds that of top foreign companies and has broad application prospects .
In the process of InP research, twinning has always been a world-class problem that restricts its industrialization and low cost, and this problem has also become an important topic in InP research worldwide. After a lot of research, reasoning and experiments, researchers from all over the world have put forward many theories on how to overcome the appearance of twins. The most influential one is the critical shoulder angle theory proposed by Professor Hurle, the former vice chairman of the International Society for Crystal Growth.
Professor Hurle believes that when growing large-diameter single crystals, choosing an appropriate shoulder angle can avoid twinning. This theory has also been recognized by international heavyweight semiconductor researchers. But is it really so?
In repeated scientific experiments, the research and development team of ZGDZ discovered the "bug" of this theory – breaking through the angle limit mentioned by Professor Hurle, it is still possible to generate twin-free crystals, and within this angle limit, it cannot be Produces 100% twin-free crystals. This situation persists even if this angle is subsequently corrected from 30° to 75°. Obviously, Professor Hurle's theory is not the final answer to the twinning problem.
Based on this revelation of the formation mechanism of twins, the team invented a flat shoulder process with shoulder angle = 90° to suppress the formation of twins by controlling the morphology of the edge of the solid-liquid interface during growth. This technology not only greatly improves the utilization rate of crystals, but the crystals produced by this process can be directly usable or close to the state of direct usability, and the yield is also greatly improved.
As a former fan of the critical shoulder angle theory, Professor Rudolph, an internationally renowned scholar, chairman of the German Society for Crystal Growth, and associate editor of the Journal of crystal growth, came to ZGDZ to witness the team's InP single crystal production process. The theoretical and practical results were greatly admired, and then he published a review article "Fundamentals and engineering of defects" ("Defect Principles and Engineering"), which spoke highly of the twinning theory proposed by the team.