Research is growing on chip materials for use in extreme environments, such as landing on Venus. On Venus, the surface temperature is around 500°C and the pressure is equivalent to the depth of Earth's oceans, which is about 900 meters. Clouds of sulfuric acid seep through the atmosphere. While GaN has attracted a lot of attention in power conversion circuits, this is just one of several applications of semiconductors in extreme environments. The high voltage, high temperature, and corrosive atmospheres found in many industrial and aerospace environments can subject equipment to conditions far beyond the operating range of silicon.
Diamond has wide band gap, high thermal conductivity, high breakdown field strength, high carrier mobility, high temperature resistance, acid and alkali resistance, corrosion resistance and radiation resistance. Its superior performance enables it to tolerate extreme conditions, and it has great application prospect in the harsh environment of high power and high voltage such as Venus.
In addition, as with all space destinations, every gram of material needed to protect components limits overall mission capability. While proper packaging can often protect components from such harsh conditions, doing so adds weight and system complexity. The original Venus lander mission design called for a 686-kilogram airtight capsule with a working life of just five hours, the team said. With the addition of diamond design modifications, its electronics can withstand the environment and weigh only 20 kilograms, most of which are batteries. And more importantly, NASA is now able to consider 60-day mission plans.
The use of diamond in semiconductors adds a different set of benefits to high temperature environments. The doping in diamond is not completely ionized at room temperature, and the carrier concentration increases with increasing temperature. This behavior is the opposite of that in GaN, making operating temperature extremely important for device performance. However, mobility decreases with increasing temperature, so diamond's electrical conductivity peaks around 150°C to 200°C. The driving current also increases as the temperature increases, but so does the leakage current.
According to the report, high temperatures reduced the on-off current ratio of mesfets from 1×108 to only about 1000. These devices are fabricated with intrinsic CVD diamond on a commercial diamond substrate, followed by p- and p+ doping layers. After etching the multifunction and source/drain layers, they made Ti/Au ohm contacts for the source and drain, and Mo/Au Schottky contacts for the grid. At MRS, MIT research applies the model developed for GaN fin FeTs to diamond-based devices. The linear power density of the modeled device reaches 7.36MW/cm2, which is about 2.7 times higher than that of similar GaN devices.
One small step for planetary exploration, one giant leap for mankind. In order to promote the wide application of diamond in the fields of aerospace, national defense science and technology, domestic and foreign research teams have carried out a large number of related studies. Focusing on the research and development and production of diamond, the company currently has products and services such as diamond hot-sink sheet/wafer grade diamond/diamond coating. High-power semiconductor laser using diamond hot-sink sheet has been used in optical communication, and has also been applied in laser diode, satellite thermal expansion plate, electronic packaging materials and other fields.