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Related Concept Videos

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...
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...
Carrier Generation and Recombination01:22

Carrier Generation and Recombination

Carrier generation is the process by which electron-hole pairs (EHPs) are created within the semiconductor. In direct-bandgap semiconductors, such as gallium arsenide (GaAs), this occurs efficiently when energy absorption prompts valence electrons to leap into the conduction band, leaving behind holes.
This process is given by the generation rate G and is efficient due to the conservation of momentum between the valence band maximum and conduction band minimum.
Indirect generation involves an...
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...
MOSFET: Enhancement Mode01:22

MOSFET: Enhancement Mode

Enhancement-mode MOSFETs are pivotal components in electronics, distinguished by their capacity to act as highly efficient switches. They are part of the larger family of metal-oxide Semiconductor Field-Effect Transistors (MOSFETs). They are available in two types: p-channel and n-channel, each tailored to specific polarity operations.
In their basic form, enhancement-mode MOSFETs are typically non-conductive when the gate-source voltage (Vgs) is zero. This default 'off' state means no current...
P-N junction01:11

P-N junction

A p-n junction is formed when p-type and n-type semiconductor materials are joined together. At the interface of the p-n junction, holes from the p-side and electrons from the n-side begin to diffuse into the opposite sides due to the concentration gradient. This diffusion of carriers leads to a region around the junction where there are no free charge carriers, known as the depletion region. The charge density within the depletion region for the n-side and p-side can be described by the...

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Laser-induced Forward Transfer for Flip-chip Packaging of Single Dies
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Published on: March 20, 2015

Semiconductor lasers without population inversion.

A Imamōglu, R J Ram

    Optics Letters
    |October 27, 2009
    PubMed
    Summary
    This summary is machine-generated.

    Researchers developed a novel scheme for lasers that operate without population inversion using quantum well intersubband transitions. This approach offers greater control over laser properties through band-gap engineering.

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    Area of Science:

    • Quantum optics
    • Semiconductor physics
    • Laser technology

    Background:

    • Traditional lasers require population inversion, a state where more atoms are in a higher energy level than a lower one.
    • Existing inversionless laser schemes often rely on atomic systems, limiting design flexibility.

    Purpose of the Study:

    • To propose and investigate a new scheme for achieving lasing without population inversion.
    • To leverage quantum well intersubband transitions for laser design.
    • To offer enhanced control over laser parameters via band-gap engineering.

    Main Methods:

    • Utilizing interferences in double-quantum-well intersubband transitions.
    • Employing band-gap engineering to tailor subband energies, coupling strengths, and decay rates.
    • Performing detailed theoretical calculations for a specific scheme.

    Main Results:

    • Demonstrated a viable scheme for lasing without population inversion.
    • Showcased the ability to engineer key parameters of the laser system.
    • Confirmed the feasibility of creating a laser that bypasses the need for population inversion.

    Conclusions:

    • The proposed scheme offers a new pathway for developing advanced laser systems.
    • Band-gap engineering provides significant design flexibility for inversionless lasers.
    • The approach is extendable to various configurations and applications.