by MCM Research. Published on 10 Nov 2021
Third generation semiconductors possess superior physical properties compared to previous generation of semiconductors
Earlier generations of semiconductors are slowly phased out as they are unable to cope with more demanding new technologies
Third generation semiconductors will revolutionise technology in the foreseeable future
This blog is part one of a semiconductor series, focused on the rising eminence of third generation semiconductors. Part two will explore the differences between GaN and SiC, and part three will deep dive into the world of GaN. Join us on the journey to explore the world of semiconductors!
With all the hype around semiconductors today, it really makes one wonder how this industry has risen to prominence once again. Modern semiconductors can trace its roots back to the mid-70s when silicon power MOSFETs had been developed to address the increasing electrical needs of our daily lives. Power MOSFETs first appeared as an alternative to bipolar transistors by being faster, more rugged, and had higher current gain. Establishing itself as the most suitable component for commercial reality in AC-DC switching power supplies for desktop computers, variable speed motor drives, fluorescent lamps etc.
As time passed, the development of new communication tools such as optic fibres, base station power amplifiers, and lasers drove the need for semiconductors that were able to accommodate higher frequency applications. Which is now known as the second generation of semiconductors based on materials like Gallium Arsenide (GaAs) and Indium Phosphide (InP).
Recent progress in technology slowly drive traditional silicone semiconductors obsolete as they are rendered ineffective in the needs of high power uses such as EVs, data centres, and renewable energy production.
However, recent progress in technology slowly drive traditional silicone semiconductors obsolete as they are rendered ineffective in the needs of high power uses such as EVs, data centres, and renewable energy production. Third generation semiconductors based on Gallium Nitride (GaN) and Silicon Carbide (SiC) save the day with their superior physical properties in seven aspects – Wide Bandgap, High Relative Permittivity, High Breakdown Field Strength, High Saturation Velocity, High Thermal Conductivity, High Electron Mobility, and High Power Density. We believe third generation semiconductors will revolutionise technology in the foreseeable future and will continue to heavily influence the growth trajectory of technological development.
The most prominent feature of third generation semiconductors is its wide bandgap compared to previous generations of semiconductors. The bandgap reflects how tightly valence electrons are bound to an atom, where higher bandgap materials require a greater amount of energy for intrinsic excitation of the valence electrons.
Semiconductors with a bandgap that’s greater than 2.3 eV is considered a wide bandgap material. The wider the bandgap, the more energy is required for electrons to travel from the valence band to the conduction band. Resulting in wide bandgap materials being able to operate under higher temperatures and voltages.
The relative permittivity reflects the dielectrics’ ability to store static energy in an electric field. The lower the relative permittivity, the lower the conductivity. A low relative permittivity is preferred in high frequency or high power applications as it prevents the build-up of static charge and crosstalk – an adverse effect that damages the electrical components in any device. Allowing a longer lifespan of semiconductors under continuous high powered use. Third generation semiconductors have a lower relative permittivity which drives greater sustainability due to its lifespan, contributing to greater environmental sustainability.
Under a strong electric field, the electric density suddenly increases when electric field strength increases. In this critical field, the dielectric will shift change from an insulator to a conductor (aka. semiconductor), also known as the breakdown of the dielectric. The greater the breakdown field strength of a semiconductor, the greater the voltage resistance of the capacitor. Third generation semiconductors with a higher breakdown field strength allows them to be suitable for high voltage applications that previous generations of semiconductors cannot endure.
Saturation velocity is the maximum velocity attained by a charge carrier (normally electrons) in the presence of very strong electric fields. When this happens, the semiconductor is said to be in a state of velocity saturation. Charge carriers normally move at an average drift speed proportional to the electric field strength they experience temporally. The proportionality constant is known as the mobility of the carrier. A good conductor would have a high mobility for its charge carriers, meaning a high velocity, and consequently higher current values for a given electric field strength. However, there is a limit to this process as a charge carrier cannot move any faster once the saturation velocity has been reached. Saturation velocity is a very important parameter in the design of semiconductor devices, especially Field Effect Transistors (FET).
Thermal conductivity of a material is a measure of its ability to conduct heat. Heat transfer occurs at a lower rate in material of low thermal conductivity than in materials of high thermal conductivity. For instance, materials with high thermal conductivity are widely used in heat sink applications, and materials of low thermal conductivity are used as thermal insulators. Third generation semiconductors have a higher thermal conductivity which allows a higher working voltage/power, leading to a more resilient conductor that won’t degrade under constant stress. Providing consistency and reliability in modern day use.
Electron mobility characterises how quickly an electron can move through a metal or semiconductor when pulled by an electric field.
Conductivity is proportional to the product of mobility and carrier concentration. For example, the same amount of conductivity can come from a small number of electrons with high mobility, or a large number of electrons with low mobility. This doesn’t affect the conductivity of metals but has a significant impact on semiconductors.
Almost always, higher mobility leads to better device performance, ceteris paribus.
Semiconductor mobility depends on the impurity concentration (including donor and acceptor concentration), defect concertation, temperature, electron and hole concertation. It also depends on the electric field, especially at high fields when velocity saturation occurs. Electron mobility can be determined by the Hall Effect, or inferred from the transistor’s behaviour. Third generation semiconductors have greater electron mobility than previous generations which gives it superior performance in high frequency applications such as telecommunications.
Power density is the amount of power per unit volume. If a system has a high power density, it can output large amounts of energy based on its volume. For example, a tiny capacitor may have the same power output as a large battery despite its size due to power density. Since they release their energy quickly, high power systems can also recharge quickly. Third generation semiconductors, especially GaN, can possess a very high power density which allows a significant reduction in the size of semiconductors creating more space for other components. An example would be more space for batteries in EVs.
In conclusion, in times of extraordinary growth in technology across a multitude of different sectors, the development of semiconductors play a fundamental role in achieving technological greatness. Defining characteristics of third generation semiconductors had begun to prove its value in its mass adoption. Third generation semiconductors will pave the way to the future and we are extremely enthusiastic for the opportunities it brings for both the scientific and investors’ community. To be continued…
EPC, Power American Institute, Mouser Electronics
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