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Related Concept Videos

Semiconductors01:22

Semiconductors

There is variation in the electrical conductivity of materials - metals, semiconductors, and insulators that are showcased with the help of the energy band diagrams.
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
Types of Semiconductors01:20

Types of Semiconductors

Intrinsic semiconductors are highly pure materials with no impurities. At absolute zero, these semiconductors behave as perfect insulators because all the valence electrons are bound, and the conduction band is empty, disallowing electrical conduction. The Fermi level is a concept used to describe the probability of occupancy of energy levels by electrons at thermal equilibrium. In intrinsic semiconductors, the Fermi level is positioned at the midpoint of the energy gap at absolute zero. When...
Metal-Semiconductor Junctions01:24

Metal-Semiconductor Junctions

The contact of metal and semiconductor can lead to the formation of a junction with either Schottky or Ohmic behavior.
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
Biasing of Metal-Semiconductor Junctions01:27

Biasing of Metal-Semiconductor Junctions

Biasing metal-semiconductor junctions involves applying a voltage across the junction. Specifically, the metal is connected to a voltage source, while the semiconductor is grounded. This technique is essential for controlling the direction and magnitude of current flow in electronic devices, including diodes, transistors, and photovoltaic cells.
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
Fermi Level Dynamics01:12

Fermi Level Dynamics

The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Biasing of P-N Junction01:16

Biasing of P-N Junction

The operation of a p-n junction diode involves various biasing conditions, including forward bias, reverse bias, and equilibrium.
In equilibrium, no external voltage is applied across the p-n junction. The depletion region is formed at the junction interface due to the diffusion of carriers, which leaves behind charged dopants, acceptors on the p-side, and donors on the n-side. These immobile charges create an electric field that prevents further diffusion of carriers. The related energy band...

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Related Experiment Video

Updated: Jun 16, 2026

Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform
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Nonlinear absorption in direct-gap semiconductors.

S S Mitra, L M Narducci, R A Shatas

    Applied Optics
    |February 16, 2010
    PubMed
    Summary

    The Keldysh model provides a better estimate for nonlinear absorption coefficients in semiconductors compared to perturbation theories. It accurately predicts two-photon absorption and band-edge absorption in materials like GaAs and InSb.

    Area of Science:

    • Solid State Physics
    • Quantum Mechanics
    • Materials Science

    Background:

    • Nonlinear optical phenomena are crucial for understanding light-matter interactions in semiconductors.
    • Accurate theoretical models are needed to predict nonlinear absorption coefficients for material characterization and device design.

    Purpose of the Study:

    • To calculate nonlinear absorption coefficients for direct-bandgap semiconductors at various wavelengths.
    • To compare the accuracy of different theoretical models, including perturbation theories and the Keldysh model.
    • To assess the predictive power of the Keldysh model for one-photon and two-photon absorption.

    Main Methods:

    • Calculation of nonlinear absorption coefficients using second-order perturbation theories (Braunstein and Basov).

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  • Application of the Keldysh model for nonlinear absorption calculations.
  • Comparison of theoretical results with experimental data for direct-bandgap semiconductors.

    • Main Results:

    • Perturbation theories yield either underestimates or overestimates of nonlinear absorption constants.
    • The Keldysh model provides absorption constants intermediate to perturbation theories.
    • The Keldysh model generally estimates the magnitude of two-photon absorption coefficients well.
    • The Keldysh model accurately predicts one-photon band-edge absorption in GaAs and InSb.

    Conclusions:

    • The Keldysh model offers a more reliable approach for predicting nonlinear absorption coefficients in semiconductors.
    • Accurate input parameters like effective band masses and dielectric constants are essential for theoretical calculations.
    • The Keldysh model shows promise for applications involving nonlinear optics in semiconductors.