Minority Carrier Lifetime (MCL) Value of Silicon Wafers 

UW Logo

What Is the MCL Value of a Pure Silicon Wafer?

Corporate researcher inquiry

“Hi, I am looking for a lab that can help measure the MCL (Minority Carrier Lifetime) of a pure silicon wafer. We’d like to measure the bulk MCL of a 4" round wafer, preferably using a non-destructive method. Target mapping: ~9 points (or 5 points: 1 center + 4 near corners). If only a single point is possible, we can consider that.”

UniversityWafer, Inc. replied

  • Please share purity details, surface condition (polished, etched, etc.).
  • How many wafers need testing? (The example request: 1 wafer.)
  • Provide a photo of the wafer box/label if available.
  • Center-point lifetime is most common; multi-point mapping may be available on request.

Reference #277641 for specs and pricing.

Learn, measure, and optimize your device performance through accurate MCL characterization. Buy now!

Get Your Quote FAST! Or, Buy Online and Start Researching Today!





MCL of 200 mm Silicon Wafers

Semiconductor physics researcher question

“Do you have the data for minority carrier lifetime of Si wafers with the following specification?”

Answer: Minority carrier lifetime of Si wafer: > 100 µs.

Reference #201773 for specs and pricing.

How to Request MCL Testing

  • Wafer diameter & type (e.g., 100–200 mm; CZ or FZ).
  • Doping type and resistivity (or “intrinsic/undoped”).
  • Surface finish (DSP/SSP), passivation if any.
  • Measurement plan (single point vs. 5-point vs. 9-point map).
  • Target lifetime range (e.g., >100 µs, >1 ms) and report format.

What Is Minority Carrier Lifetime (MCL)?

Minority carrier lifetime (MCL) is a key semiconductor parameter that represents the average time a minority carrier—an electron in p-type material or a hole in n-type material—exists before recombining with a majority carrier. The longer this lifetime, the longer the carrier can contribute to current flow or energy conversion before disappearing.

Understanding Carriers in Semiconductors

Semiconductors conduct electricity through two carrier types:

  • Electrons — the majority carriers in n-type silicon.
  • Holes — the majority carriers in p-type silicon.

Minority carriers are the less abundant type in each semiconductor. Their movement, lifetime, and recombination behavior determine key electrical and optical characteristics in devices.

Why Minority Carrier Lifetime Matters

  • Solar Cells: Longer lifetimes improve photovoltaic efficiency by allowing more carriers to reach junctions before recombining.
  • Bipolar Junction Transistors (BJTs): Performance and gain rely on efficient minority carrier transport.
  • LEDs and Lasers: Carrier recombination affects light output and quantum efficiency.
  • Power Devices: Reducing recombination minimizes power loss and improves switching performance.
  • Reliability: Optimized lifetimes reduce hot spots and improve device longevity.
9-Point Minority Carrier Lifetime
9-point Minority Carrier Lifetime mapping on silicon wafer

Factors Influencing Minority Carrier Lifetime

  • Doping Level: Higher doping introduces more recombination centers, reducing lifetime.
  • Impurities and Defects: Metallic contaminants like Fe, Cu, or Au can drastically shorten MCL.
  • Crystal Quality: Float Zone (FZ) silicon generally exhibits longer lifetimes than Czochralski (CZ) due to lower oxygen content.
  • Surface Conditions: Oxides or rough surfaces can accelerate surface recombination.

Typical Minority Carrier Lifetime Values

Intrinsic (Undoped) Silicon

In high-purity, undoped silicon, minority carrier lifetime can range from microseconds (µs) to several milliseconds (ms), depending on crystal quality and surface passivation.

Doped Silicon

For doped silicon, MCL decreases significantly with doping concentration. Typical commercial wafers exhibit lifetimes of a few microseconds to hundreds of microseconds, influenced by dopant type, contamination, and processing history.

Measurement Techniques

  • Quasi-Steady-State Photoconductance (QSSPC) — non-contact photoconductance decay method widely used for wafer-level testing.
  • Time-Resolved Photoluminescence (TRPL) — optical technique for ultra-clean or thin-film materials.
  • Microwave Photoconductance Decay (µ-PCD) — measures decay rate after pulsed excitation, common in R&D.

Minority Carrier Lifetime in Float Zone (FZ) Silicon

Float Zone (FZ) silicon offers superior purity and minimal oxygen contamination, resulting in exceptionally long minority carrier lifetimes. Below is a case example based on a real R&D request received by UniversityWafer.

R&D Engineer’s Request

“We would like to order 25× DSP, n-type, FZ, 100 mm, (100), 275 µm and 100× DSP, n-type, FZ, 150 mm wafers with:

Resistivity < 3 Ω·cm, Minority Carrier Lifetime (ms): > 5.8 (4”) / > 13 (6”), Thickness 280 ± 10 µm, TTV < 3 / < 1.5 µm, Bow < 2 / < 3.5 µm.”

UniversityWafer Response

Meeting such tight geometric specifications (TTV, bow, thickness) is possible but costly. The specified carrier lifetime at <3 Ω·cm resistivity is challenging, as heavy doping greatly shortens lifetime.

Example data from available FZ ingots:

  • 100 mm FZ Si — ρ = 0.98–1.02 Ω·cm → Lifetime not measured; reference ingot (ρ = 110 Ω·cm) = 11,558 µs
  • 150 mm FZ Si — ρ = 1.01–1.02 Ω·cm → Lifetime ≈ 1,571 µs
  • 150 mm FZ Si — ρ = 16.8 Ω·cm → Lifetime ≈ 14,467 µs

These examples show how increased doping (lower resistivity) significantly reduces lifetime. When requesting wafers, clarify acceptable ranges for both resistivity and MCL to balance feasibility and cost.

Request a Fast Quote

Request a quote for intrinsic or doped silicon wafers with measured minority carrier lifetime data. Float Zone, Czochralski, or epi options are available for solar, detector, and transistor research.