IGZO vs a‑Si: Which TFT technology should I choose for my X‑ray detector?
Written by Milja Kurkela, Application Engineer at Detection Technology | 30 April 2026
The choice between IGZO and a‑Si TFT technology has a direct impact on image quality, dose performance, frame rate, and long‑term reliability of X‑ray detectors. Both technologies are well established, but they are optimized for different application needs.
This application note serves as a practical guide for system designers who are evaluating X-ray detector technologies. It provides clear insights on when IGZO is the optimal choice and in which scenarios a‑Si remains the preferred solution, helping you make informed decisions tailored to your application’s requirements.
What is the difference between IGZO and a‑Si TFT technology?
The key technical difference between IGZO and a‑Si lies in electron mobility and leakage behaviour, which directly affect how charge is read from each pixel.
a‑Si TFTs
- Mature and widely deployed technology
- Predictable long‑term stability
- Proven performance in high‑dose and industrial environments
- Well suited for moderate frame rates and larger pixel sizes
IGZO TFTs
-
- Significantly higher electron mobility
- Lower off‑state leakage current
- Enables faster pixel readout and lower electronic noise
- Designed for applications with higher performance demands
These characteristics influence detector performance most strongly in dynamic and low‑signal imaging scenarios.
When should I consider IGZO for my application?
IGZO should be considered when detector performance is limited by TFT speed or noise rather than by scintillator or system design.
IGZO is typically recommended when:
- Low‑dose image quality is critical, such as in CBCT or some high‑end C‑arm systems
- Very small pixel sizes are required, typically below 100 µm
- High frame rates are needed, and a‑Si line times become a limiting factor
- The application involves dynamic imaging, where fast and clean charge readout is essential
In these cases, IGZO’s higher mobility supports faster readout and improved performance, especially when electronic noise dominates image quality.
Key takeaway: IGZO is best suited for applications that push the limits of low dose, speed, or pixel size.
When is a‑Si still the better choice?
Despite newer alternatives, a‑Si remains the preferred technology in many real‑world applications where robustness and long‑term predictability matter more than peak performance.
Amorphous Silicon is typically the better choice when:
- Pixel size and frame rate requirements are well within a‑Si capabilities
- Long‑term stability and low drift are important
- The system operates in high‑dose or high‑energy environments, especially in industrial imaging
- Proven radiation hardness is required
- Cost efficiency and manufacturing maturity are key decision factors
For many industrial and standard medical systems, a‑Si continues to offer a reliable and well‑understood solution.
How should radiation hardness influence my technology choice?
Radiation performance is an important consideration, especially in industrial and high‑energy imaging environments.
- a‑Si benefits from decades of field evidence demonstrating excellent radiation hardness, including reliable operation beyond 1 MRad in demanding environments.
- IGZO has demonstrated promising radiation tolerance and continues to improve, but long‑term field data in harsh radiation conditions is still more limited compared to a‑Si.
For applications where radiation hardness is a primary requirement, a conservative, evidence‑based approach is recommended.
Key takeaway: Technology selection for radiation‑intensive environments should be guided by proven long‑term field data.
How do I decide which technology is right for my X‑ray detector?
The most reliable way to choose between IGZO and a‑Si is to start from application requirements.
- Choose IGZO if your system demands:
- Low‑dose performance
- Small pixel size
- High frame rate or fast readout
- Choose a‑Si if your system prioritizes:
- Proven durability and radiation hardness
- Long‑term stability
- Cost‑effective and mature technology
Both technologies address different needs and continue to coexist in modern X‑ray imaging systems.
Read the full IGZO vs a‑Si application note
This page is based on the application note “IGZO versus a‑Si: TFT Technology Performance Comparison”, which provides a detailed technical comparison of material properties, pixel design, imaging performance, drift behaviour, and radiation considerations.