With greater voltage breakdown, faster switching speeds and higher current limitations, wide bandgap semiconductors are gaining in market application over silicon devices. Silicon carbide (SiC) and gallium nitride (GaN) semiconductors can increase the efficiency of modern power electronics as well as reduce their footprint.
Ponder this: In high radiation environments such as deep space and low Earth orbit (LEO) space applications, where silicon-based semiconductors degrade rapidly, wide bandgap semiconductors now are poised to disrupt the market, according to studies such as a 2021-2026 projection of the space power electronics market issued by MarketsandMarkets.
GaN and SiC power semiconductors are expected to change the power industry landscape within the next decade and will have a consolidated share of 13 percent in the power semiconductor market by 2024, according to the MarketsandMarkets study, which expects the space power market to grow from USD 205 million in 2021 to $435 million by 2026, at a CAGR of 16.2 percent.
Higher Temperature and Radiation Challenges
Why? For starters, these wide bandgap materials can operate at higher temperatures of up to 200°C while silicon is limited to 150°C. A wide bandgap semiconductor also can handle nearly 10 times more voltage as compared to silicon and the switching speed/switching frequency of SiC and GaN are also nearly 10 times higher than silicon.
In space, ionizing radiation primarily takes the form of charged particles and x-ray radiation. In LEO and other space apps, the dominant forms of radiation are heavy atomic nuclei, protons, alpha and beta particles and high-energy photons from intensive solar events.
In ionizing radiation, the radiation energy of particles or high-energy electromagnetic radiation passes through the semiconductor material used to produce electronic components. The radiation energy gets transferred to the electrons and nucleus of semiconductors and ruptures the chemical bonds, which leads to ionization and atomic displacement. In turn, this introduces changes in electronic component characteristics and can even damage the components.
Space application concerns include
- Total ionizing dose (TID), basically chronic exposure to radiation
- Displacement damage dose (DDD), which is the structural damage imparted on the crystal lattice of the device by highly-energetic particles. In some cases, such as silicon carbide Schottky diodes, the SiC parts are relatively DDD-robust.
- Proton-induced single-event effects (SEE) are the dominant particle for low earth orbits and the major component from solar particle events
Radiation Resistance
The resistance to radiation, called radiation hardness, protects against damage caused by radiation from high-energy rays and particles. Silicon-on-insulator (SOI) or silicon-on-sapphire (SOS) are typical bases for radiation hardening. Space-grade SOI and SOS chips can survive radiation exposure levels between (100 and 300 krad). Bipolar integrated circuits generally have higher radiation tolerance than CMOS circuits and as such are commonly used in the manufacturing of radiation tolerant components.
Electronics that employ wide bandgap semiconductors promise better resistance against radiation damage over conventional silicon-based electronics. So, what is the new normal? Penn State University is leading a $7.5 million Defense Multidisciplinary University Research Initiative Award that promises to better predict and mitigate radiation-induced damage of wide bandgap semiconductors. Rongming Chu, an Associate Professor of Electrical Engineering, will spearhead the project.
According to Chu, wide bandgap semiconductors are promising candidates for building electronics used in environments with significant radiation, such as outer space. With higher breakdown strength, lower gate charge, lower switching losses, better thermal conductivity and low on-resistance, power devices based on GaN significantly outperform silicon-based devices and enable more compact and lighter weight circuitry for critical spaceborne missions.
Preliminary studies have indicated that the radiation resistance appears to be limited by defects in the semiconductors, rather than by the material’s intrinsic properties, explains Chu. “In this project, we seek to understand the radiation effects of these defects so that we may develop a strategy to redesign the wide bandgap semiconductor device for the ultimate radiation hardness,” he said.
New Products
Semi companies are preparing for what comes next. Efficient Power Conversion Corp. (EPC) has expanded its family of radiation-hardened gallium nitride (GaN) products for power conversion solutions in critical space and other high-reliability environments with a 100V device that has a low on-resistance.
EPC Space‘s EPC7004 radiation-hardened GaN FET is a 100V, 7 mΩ, 160 in a 6.56 mm2 footprint. The EPC7004 has a total dose radiation rating greater than 1 Mrad and SEE immunity for linear energy transfer (LET) of 85 MeV/(mg/cm2). The EPC7004 joins a family of rad hard products than range from 40V to 200V, offering significant electrical and radiation performance benefits for applications including DC-DC power, motor drives, lidar, deep probes and ion thrusters for space applications, satellites and avionics.
The EPC7004, along with the rest of the Rad Hard family (EPC7014, EPC7007, EPC7019 and EPC7018) are offered in a chip-scale package, the same as the commercial eGaN FET and IC family. Packaged versions will be available from EPC Space.
Here are more juicy details about the EPC7018. It is a 100V, 3.9 mΩ, 345 A rad-hard GaN FET in a 13.9 mm2 footprint. Applications benefiting from the performance and deployment of the EPC7018 include DC-DC power, motor drives, lidar, deep probes and ion thrusters for space applications, satellites and avionics.
Mounting demand in the radiation-hardened component arena is due in part to the success of lower-cost space applications like small satellites and LEO constellations or satellites.
Made possible by the lower cost of launches, the space industry now sees a rush to deploy satellite constellations. These small, lightweight devices (up to a few hundred kilos) operate typically in LEO at altitudes from 400 to 2000 kilometers. They focus on various objectives including internet access and Earth observation missions. The resulting manufacturing flow is largely based on AEC-Q100 / AEC-Q101 specifications but also includes specific design and manufacturing variations for space application.
LEO satellites receive more atmospheric protection and are exposed to lower levels of radiation than traditional satellites launched into higher earth orbits. In addition, they are designed for shorter lifetimes. The expected lifetime for satellites in LEO is about five years, significantly lower than the 10- to 20-year requirements of a geostationary orbit satellite. As a result, the level of immunity required is lower.
In addition to tests for total ionization dose (TID), total non-ionization dose (TNID) and single-event effect (SEE), STMicroelectronics’ LEO space components benefit from a Certificate of Conformance, aimed at approving flight-ready components, without any additional cost, lead time or risk for aerospace manufacturers and service providers.
The new STMicro series ensures a radiation hardness match to the LEO mission profile, with a total ionization dose immunity up to 50 krad (Si), high immunity to total non-ionizing dose and single event latch-up (SEL) immunity up to 62.5MeV cm²/mg. The parts are assembled on the same production line used for ST’s AEC-Q100 automotive-qualified ICs, allowing the LEO series to benefit from the statistical process control that enables high-volume, high-quality production.
Aerospace platforms also require reliable, secure and robust memory solutions capable of meeting strict performance and environmental metrics. These compute-intensive applications put increasing demands on memory performance and density to handle the large amounts of data sourced from multiple sensors and processor nodes.
Infineon Technologies has announced the availability of the space industry’s first radiation-hardened serial interface ferroelectric RAM (F-RAM) for extreme environments. The new devices are more energy efficient than non-volatile EEPROM and serial NOR flash devices for space applications.
The addition of a qualified manufacturers list (QML) class Q qualification F-RAM to Infineon’s memory portfolio makes the benefits of large endurance, non-volatile write technology and over 100-year data retention available to space applications. As a direct replacement for serial NOR flash and EEPROMs, a rad hard F-RAM is well-suited for data logging of mission critical data, telemetry storage and command and control calibration data storage. The new device is also ideal for providing boot code storage solutions for microcontrollers, FPGAs and ASICs.
GaN FETs are a very good fit for satellite applications but require a good gate driver to realize their full potential. With enhancement mode gallium nitride (GaN) FETs availability together with a radiation tolerant PWM controller and GaN FET driver, GaN deployment in power management applications for space can be realized.
For example, the Renesas ISL70040SEH and ISL73040SEH Low Side Gallium Nitride (GaN) Field Effect Transistor (FET) Drivers and ISL70023SEH and ISL70024SEH GaN FETs enable primary and secondary DC/DC converter power supplies in launch vehicles and satellites. These devices power ferrite switch drivers, motor control driver circuits, heater control modules, embedded command modules, 100V and 28V power conditioning and redundancy switching systems.
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