Silicon (Si) vs Germanium (Ge) Substrate Compared

Silicon versus Germanium

Why is silicon wafers preferred over Germanium wafers?

Germanium was in the first transistors. These transistors were meant to replace the vaccum tubes found in World War Two era Radar. The military wanted smaller, lighter and more powerful radar to bomb Germany.

But the ware ended and the military's, spare-no-cost, attitude became more frugal.

With the research open to the public, commercial entities discovered that Silicon worked very well in consumer items such as portable transistor radios. Thus Silicon, which is more abundant and less expensive than Germanium became the standard material and is still being used today and for the foreseable future.

Silicon Benefits:

Low Reverse Leakage Current
Good Temperature Stability
Low Cost
High Reverse Break Down Voltage
Large Forward Current

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Germanium Semiconductor

The current trend is to use silicon instead of germanium, but what could be the reason? As we all know, silicon and germ are semiconductors and are among the most common materials in the world.

The Pros and Cons of Germanium Semiconductors and Why?

Germanium (Ge) was one of the first materials used in semiconductor devices before silicon became dominant. While it's not as widely used today, it still has some compelling properties that make it relevant in niche applications. Here's a breakdown of the pros and cons of germanium semiconductors, along with the reasoning behind each point:

✅ Pros of Germanium Semiconductors

High Carrier Mobility
- Why: Germanium has higher electron and hole mobility compared to silicon. This means charge carriers can move faster through the material.
- Benefit: Enables faster switching speeds in transistors, which is great for high-frequency and analog applications.
Low Band Gap (0.66 eV)
- Why: Germanium’s small band gap makes it easier to excite electrons into the conduction band.
- Benefit: More sensitive to infrared light, which is useful for photodetectors and IR sensors.
Excellent Compatibility with Silicon
- Why: Germanium can be grown on silicon substrates (e.g., in SiGe or Ge-on-Si devices).
- Benefit: Can be integrated into existing silicon fabrication infrastructure, especially for CMOS-compatible devices.
Good for Tunnel FETs and Spintronics
- Why: The low effective mass of carriers and narrow band gap support tunneling phenomena.
- Benefit: Promising for next-gen low-power electronics.

❌ Cons of Germanium Semiconductors

Higher Leakage Currents
- Why: The low band gap leads to higher intrinsic carrier concentration, increasing leakage.
- Drawback: Worse performance in digital circuits due to power loss and noise.
Thermal Instability
- Why: Germanium oxidizes poorly and doesn’t form a stable native oxide like silicon dioxide (SiO₂).
- Drawback: Difficult to make reliable insulating layers, which limits use in MOSFET gate dielectrics.
More Expensive and Less Abundant
- Why: Germanium is less abundant and more costly to refine compared to silicon.
- Drawback: Not cost-effective for large-scale applications like solar panels or mainstream chips.
Lower Breakdown Voltage
- Why: Due to its small band gap and higher dielectric constant.
- Drawback: Less suited for high-power or high-voltage applications compared to silicon or SiC.

⚖️ Use Cases Where Germanium Excels

High-speed RF transistors (e.g., SiGe BiCMOS)
Infrared detectors and night vision
Photovoltaics (multi-junction solar cells)
Research in quantum computing and low-power logic

Would you like a comparison between Ge, Si, and GaAs or how Ge fits into future technologies like quantum computing or AI hardware?

🔬 Comparison: Germanium (Ge) vs Silicon (Si) vs Gallium Arsenide (GaAs)

Property	Germanium (Ge)	Silicon (Si)	Gallium Arsenide (GaAs)
Band Gap (eV)	0.66	1.12	1.42
Electron Mobility (cm²/V·s)	~3900	~1500	~8500
Hole Mobility (cm²/V·s)	~1900	~450	~400
Thermal Conductivity	Lower	High	Lower than Si
Native Oxide Quality	Poor	Excellent (SiO₂)	Poor (Ga₂O₃ is unstable)
Cost	High	Low	High
Breakdown Voltage	Low	High	Medium
Optoelectronic Use	Good for IR	Poor (indirect band gap)	Excellent for LEDs, lasers
Common Applications	IR detectors, SiGe HBTs	Microprocessors, solar	High-speed RF, LEDs, lasers

🔎 Summary:

Germanium: High mobility, low band gap — great for speed and photodetection, but not thermally stable or cost-efficient for general use.
Silicon: Balanced performance, cheap, mature infrastructure — king of digital and power electronics.
Gallium Arsenide: Great for optoelectronics and RF, but brittle, expensive, and hard to fabricate at scale.

🔮 Germanium in Future Technologies

1. Quantum Computing

Why it's useful: Germanium has high-quality epitaxy and supports quantum dot formation with long spin coherence times (especially Ge/SiGe systems).
Example: Quantum dots in Ge allow for electrically-controlled spin qubits — a hot research area.

2. AI Hardware & Neuromorphic Computing

Why it's useful: High mobility supports ultra-fast transistor switching; its integration into SiGe platforms could support analog computation or specialized accelerators.
Challenge: Needs better thermal and dielectric solutions for scalability.

3. Tunnel FETs (TFETs)

Why it's useful: Ge’s low band gap and light effective mass make it excellent for tunneling-based low-power transistors.
Benefit: Could drastically reduce leakage current and power consumption in future AI edge devices.

Why is Silicon Better Than Germanium?

Silicon crystals have fewer free electrons than germanium crystals at room temperature, which is why silicon crystals are used for semiconductor devices.

In general, the ICBO of germanium is 10-100 times greater than that of silicon, but the variation of ICBo at any temperature is lower for silicon than for germanium. This means that silicon will have a higher ICBI (Inter - Cell Boundary Boiling Point), but a rough rule of thumb - of - thumb with germanium bebe says that the ICBO doubles at the same temperature.

Why Most Semiconductor Devices are Made by Silicon Compared to Germanium

Silicon can work up to 150 degrees Celsius, and therefore excess heat does not damage its components so easily. The maximum normal working temperature for g-germanium is 70 degrees Celsius and the structure of germanium is destroyed at about 100 degrees Celsius.

The PIV value of a silicon diode is almost 1000 V, while it is higher than that of g-germanium diodes. The Piv values for germanium diodes are closer to 400 V and for silicon to about 500 - 600 V.

The disadvantage of silicon compared to germanium is that the preload of the silicon diodes is higher than that of the germanium diodes. This means that high preload is required for high-performance applications such as solar cells, photovoltaics and energy-saving computers.

Silicon crystals contain fewer free electrons than germanium crystals at room temperature, and this is why the modern trend towards silicon semiconductors is going. The disadvantages of silicon have been eclipsed by the other advantages over silicon mentioned above. So why is silicon g - germanium preferred and why are silicon and g germanium both preferred?

The variation of the collector cross-section temperature is lower in silicon than in germanium. This means that silicon has a much smaller collector and thus a higher power output.

The structure of germanium crystals is destroyed at high temperatures, but silicon crystals are not easily damaged by excess heat. The peak voltage values of silicon diodes are greater than those of germanium diodes. Silicon is also cheaper due to the greater abundance of the element and its lower electricity consumption.

There is a lot of sand in nature, and sand is one of the most abundant elements in the earth's crust and a good source of energy.

The first transistors were made with germanium (Ge) and the potential barrier of silicon is greater than that of g germanium. After considering all the advantages listed above, we can conclude that silicon was the best element for semiconductor devices and applications. But what disadvantages does silicon have compared to germ and what advantages does it have compared to silicon?

Why is Silicon Mainly Used in Tech Companies Than Germanium?

The most important question to ask is, "Why is silicon mostly used in tech companies than germanium?" silicon versus germanium explained Neither element is as pure as the other, so silicon is a good choice for computer chips. Its high purity allows it to grow into an insulating oxide when heated in a furnace. This property is important for the transistors in our devices. And, unlike germanium, silicon is inexpensive.

Silicon has special properties that make it ideal for electronics. It's cheap and scalable for large production facilities. It is a semiconductor material, which means it can have different levels of conductivity. It also has a low density, which makes it easier to use in devices and electronics. Its crystalline structure makes it an excellent choice for semiconductors. Furthermore, silicon is conductive to electrons, so it's perfect for use in semiconductor devices.

Despite its low cost, silicon is a superior semiconductor material. It's the basis of almost every computer chip. It's cheaper than gold or silver and scales well to large production facilities. The only problem with silicon is its inefficiency in converting light to an electrical signal and vice versa. This is why it's so popular in computer processors connected by metal wires.

One of the best reasons to choose silicon over germanium is its superior thermal stability. This is due to its higher melting point, which allows it to function better in hot conditions. While germanium has a greater electrical conductivity, its insulating properties make it a poor choice for most consumer electronics. So, which is better? You may be wondering: Which is better? If you're buying a new chip, you should definitely consider using silicon.

Silicon is a great semiconductor material. The only disadvantage of using silicon is that it costs more than germanium. Other semiconductors, like germanium, have a lower conductivity. However, they do not work well with light, so you shouldn't use silicon to create one. It's just not practical. So, if you're not a techie, you may not be able to use germaniun to make the same type of product, you can always use the other material.

It's also important to remember that silicon is cheaper than germaniun. It's also easier to process. It's less expensive to process than germanium. It's also cheaper. You can't just buy it in stores. It's also easier to use it at home. You can also buy it from online retail. This is a better option than germaniun.

Why is silicon used more than germaniun? The reason is simple. It has a higher electrical resistance than germaniun. But because of its lower electrical resistance, it's more expensive than silicon. That's why germaniun is more efficient than its sibling, but it is not as durable. If you're a techie, you'll want to know why it's the best choice.

Silicon is the most popular material in today's electronics. It's an insulator that's compatible with light. It's the most popular choice for semiconductors. Its high electrical resistance makes it an excellent choice for electronics. It's also cheaper than germaniun, making it more appealing to the tech industry. It is also much cheaper than germaniun, so it's an obvious choice.

The main reason for silicon's use in electronics is its high-temperature resistance. This is important in the case of transistors. As a result, it's more stable than its counterpart, which makes it more reliable. If you're a tech company, you want to make sure that your chips work well in extreme temperatures. If you're not familiar with how to choose the right materials for your products, you should know that there are many reasons why.

Silicon is widely used because of its high thermal resistance. The other main reasons for using silicon are its high availability and ease of fabrication. This is why silicon is more widely used in tech companies than germaniun. Compared to germaniun, silicon is less expensive. In addition to its lower cost, silicon is easier to process. And it is more stable at higher temperatures. The reason why it's more popular is because it's more valuable than germaniun.

Silicon Verus Germanium It's All About the Melting Point

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Germanium vs Silicon Performance

We demonstrated the first silicon germanium transistor, which operates at frequencies up to 500 GHz. Our Germanium substrate invention refers to so-called band transistors and includes a heterojunction field - effect transistors made of silicon, germanium, silicon and carbon alloys. The present invention relates to a semiconductor device structure made of a silicon-based channel layer and consisting of a silicon carbon alloy with a carbon layer and a single silicon layer. We have linked our invention to the development of the so-called "Band Engineered Transistor" (BTR) and its application in the field of field effect transistors. [Sources: 1, 3]

A mixture of germanium and silicon is placed next to a layer of pure silicon, which causes the silicon atoms to stretch and align with the g-germanium atoms. This is called electron mobility, and although the electrons in silicon are quite mobile, they are much more so in the presence of arsenic. The arsenic-doped silicon can be called "N-type silicon" because it adds electrons to generate an electric current when a voltage is applied to the diode. While the silicon particles move from one layer to another in a very short time, this is called "electron mobility," and while the electron in silicon is quite "mobile," it moves much faster in front of the diodes. [Sources: 6, 9, 11]

Silicon has been successfully researched to replace or work with it, and it works well in a variety of applications, such as solar cells, solar panels, batteries and other electronic devices. [Sources: 8]

A MOSCAP-based silicon photonics modulator is a device so-called because it is the first of its kind in the world to consist of a silicon-germanium photonics module with high performance and low power consumption. In [4] we show that the substrate can be made of silicon and the resulting germanium, as well as a combination of the two materials. [Sources: 2]

Silicon is much harder to process than germanium and offers great prospects for better performance, especially in changing applications. One of the reasons why silicon was selected for the MOSCAP photonics modulator in the first place over g germanium is that silicon works at a higher temperature, while the bond between electrons in silicon is stronger than in gGermanium. Fluctuations in collector separation of electricity and temperature are also lower than in Germania, and silicon offers a great prospect for better performance, especially in switching applications. [Sources: 4, 8, 13]

Advantages of Silicon over Germanium

Silicon also has a major advantage: The native oxide silicon dioxide forms a stable and easy to form stable, easy to form and stable thin film. Silicon and germanium thin films can easily be up to 1 mm or up to 2 mm thick, so the gains in silicon transistors are much greater than in gGermanium devices with the same number of electrodes. N-type when the material is amorphous, which promotes saturation and reduces the amount of power that is kept constant for other factors. With the current required for a GST-2 device, both the silicon and Germania devices can be with identical surface area of the transistor, the efficiency increases by a factor of 1.5. [Sources: 0, 5, 7, 14]

The main difference between g-germanium and silicon diodes is the voltage at which electric current flows freely through the diode. If you are a PNP or NPN transistor, the VBE of the small gGermanium circuit is about 0.3 volts, which is much less than that of a silicon transistor, while the silicon is about 0.7 volts. Silicon diodes require more voltage to conduct a current, and it takes between 0 and 7 volts to produce a forward and forward tilt in silicon diodes, but the primary differences between silicon and g-germanium diodes are in the voltages required for the diode to switch on and forward. [Sources: 0, 9]

The MAX2641 silicon germanium provides a silicon bipolar lna that falls below NF at frequencies approaching the 2GHz limit, while the ggermanium does not. [Sources: 14]

Why we use Silicon Instead of Germanium?

Germanium sounds a bit different from silicon in a certain circuit, but it is also worth noting that many excellent-sounding pedals use silicon components. It is much cheaper to create circuits from silicon than with other semiconductors, because silicon is not the only semiconductor material that exists. The electron hole mobility of silicon was very low and constitutes an obstacle to high performance, although manufacturers have increased it by incorporating germanium into silicon. This could also change with the 1S130 silicon diode, which has been in use for several years. [Sources: 0, 10, 11, 13]

Both silicon and germanium can overcome this deficiency by proposing a more efficient method of measuring power density and a higher mobility of electron holes than silicon. [Sources: 5]

Germanium vs Silicon Transistors

What is the advantage of silicon over germanium for transistor fabrication? In simulations, Saraswats group has shown that germanium transistors are significantly better than silicon in the nanometer range. In just a few years, g Germanium will be a serious player in the semiconductor sector. The future of electronics is bright and it is largely silicon-based, but silicon comes in many different flavors and its performance differs from one to the other in terms of power, power density and efficiency. But the future of electronics is brighter, and it is largely silicon-based, but silicon is available in many different flavors, and its performance varies from one of the world's most important semiconductor companies, Intel, which has been heavily involved in the development of silicon technology. [Sources: 11, 12]

Sources:

[0]: https://electronics.stackexchange.com/questions/323393/does-it-matter-if-i-replace-germanium-transistors-with-silicon

[1]: https://www.eurekalert.org/pub_releases/2006-06/giot-gtt061706.php

[2]: https://www.hindawi.com/journals/jnm/2018/2497352/

[3]: https://patents.google.com/patent/EP1543565A4

[4]: https://www.britannica.com/technology/transistor/Silicon-transistors

[5]: https://www.intechopen.com/books/new-research-on-silicon-structure-properties-technology/silicon-germanium-sige-nanostructures-for-thermoelectric-devices-recent-advances-and-new-approaches-

[6]: https://www.arnnet.com.au/article/5715/ibm_triples_transistor_performance_germanium/

[7]: https://medium.com/@sixsamuraisoldier/why-gaas-and-iii-vs-probably-wont-replace-silicon-568b4701901d

[8]: http://www.eeherald.com/section/news/onws20150111001a.html

[9]: https://sciencing.com/characteristics-silicon-germanium-diodes-6823105.html

[10]: https://robertkeeley.com/2013/09/germanium-transistors/

[11]: https://www.sheffield.ac.uk/news/nr/next-electronics-revolution-silicon-1.498610

[12]: https://engineering.stanford.edu/magazine/article/small-scale-transistors-calls-revival-silicon-rival

[13]: http://scienceline.ucsb.edu/getkey.php?key=4527

[14]: https://www.maximintegrated.com/en/design/technical-documents/app-notes/6/697.html

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Chart Comparing Substrates Semiconductor Properties and Future Potential

A chart summarizing the key properties and future tech applications of Germanium, Silicon, and Gallium Arsenide for quick comparison, followed by a deep dive into SiGe BiCMOS and Ge-based quantum dots.

Comparison Table: Semiconductor Properties & Future Potential

Property / Use Case	Germanium (Ge)	Silicon (Si)	Gallium Arsenide (GaAs)
Band Gap (eV)	0.66 (direct/indirect)	1.12 (indirect)	1.42 (direct)
Electron Mobility	~3900 cm²/V·s	~1500 cm²/V·s	~8500 cm²/V·s
Hole Mobility	~1900 cm²/V·s	~450 cm²/V·s	~400 cm²/V·s
Thermal Conductivity	Low	High	Moderate
Native Oxide Stability	Poor (GeO₂ is water-soluble)	Excellent (SiO₂ is robust)	Poor (Ga₂O₃ not ideal)
Infrared Sensitivity	Excellent	Poor	Moderate
Photonic Devices	Good (IR detectors, some lasers)	Poor (indirect gap)	Excellent (LEDs, lasers, photodiodes)
Quantum Dot Compatibility	Excellent	Moderate	Rare
CMOS Integration	Compatible via SiGe/Ge-on-Si	Native	Incompatible
Cost & Scalability	Expensive	Very Cheap	Expensive
Future Roles	Quantum computing, TFETs	Mass CMOS, power devices, AI cores	RF, optoelectronics, high-speed logic

🔬 Deep Dive 1: SiGe BiCMOS (Silicon-Germanium Bipolar CMOS)

Why Use SiGe?

SiGe (Silicon-Germanium alloy) allows for bandgap engineering and strain tuning in transistors.
The heterojunction bipolar transistors (HBTs) created using SiGe offer:
- Higher speed
- Lower noise
- Lower power consumption
- Better high-frequency performance compared to standard CMOS

Use Cases:

5G wireless, radar, automotive LIDAR, high-speed ADCs
IBM, GlobalFoundries, and Intel have all developed SiGe BiCMOS nodes for mixed-signal applications.

🔬 Deep Dive 2: Germanium-Based Quantum Dots

Why Germanium?

Quantum dots made from strained Ge or Ge/Si core-shell structures can host electron or hole spin qubits.
Ge has:
- High mobility for fast gate control
- Long spin coherence times (important for qubit stability)
- CMOS-compatible fabrication via Ge/SiGe heterostructures

Emerging Research:

QuTech (Netherlands), TU Delft, and IBM Research are actively exploring Ge qubits.
Ge-based platforms can potentially scale better than GaAs quantum dots, which suffer from hyperfine noise due to nuclear spins.