Substrates Used For Photoexcitation Research

university wafer substrates

CdSe Wafers for Photoexcitation 

A Postdoctoral Research Scientst requested a quote for the following:

Question:

We are interesting in procuring a wafer of Cadmium Selenide (CdSe) for photoexcitation charge imaging in a scanning ultrafast electron microscope. A 1-2" wafer would be best. Is this possible?

Answer:

  • CdSe single crystal substrate, (10-10) 10x10x1.0mm,2sp Low Resistivity
  • CdSe single crystal substrate, (10-10) 10x10x1.0mm,2sp High Resistivity

Reference #282608 for specs and pricing.

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What is the Effect of Light on a Semiconductor?

Light can significantly affect the properties of a semiconductor through a process called photoexcitation, where photons interact with the material. The effects depend on the semiconductor material, the wavelength of the light, and the experimental conditions. Here are the primary effects of light on a semiconductor:

1. Generation of Electron-Hole Pairs

  • When a photon with energy greater than or equal to the bandgap energy of the semiconductor is effects of light on a semiconductor, highlighting the generation of electron-hole pairs and their movement, leading to increased conductivityabsorbed, it excites an electron from the valence band to the conduction band.
  • This creates an electron-hole pair (e.g., a mobile electron in the conduction band and a hole in the valence band).
  • The number of electron-hole pairs generated depends on the intensity and energy of the incident light.

2. Change in Electrical Conductivity

  • The generation of free charge carriers increases the electrical conductivity of the semiconductor, a phenomenon called photoconductivity.
  • This property is used in photodetectors and solar cells.

3. Photovoltaic Effect

  • In materials with a built-in electric field (such as p-n junctions in solar cells), the photoexcited charge carriers are separated, generating a voltage or current.
  • This is the basis for converting light into electrical energy in solar panels.

4. Photo-induced Recombination

  • After a certain time, the electron-hole pairs recombine, releasing energy in the form of heat or light (depending on the material properties).
  • The recombination rate depends on the quality of the material, the presence of defects, and doping levels.

5. Thermal Effects

  • Absorption of light can also increase the temperature of the semiconductor, altering its resistivity, carrier mobility, and other properties.

6. Bandgap Modification (Nonlinear Effects)

  • At very high light intensities, nonlinear optical effects may occur, such as bandgap narrowing or two-photon absorption.
  • These effects are prominent in advanced laser applications and optical modulators.

Applications Leveraging These Effects:

  • Photodetectors: Use the change in conductivity or generation of photocurrent.
  • Solar Cells: Convert light into electricity through the photovoltaic effect.
  • Optoelectronic Devices: Include LEDs and lasers where recombination emits light.
  • Biosensors: Detect biochemical interactions by monitoring light-induced changes in the semiconductor.

Would you like more details on any specific application or effect?