Mott Variable Range Hopping

Definition

Mott variable range hopping is a conduction mechanism in disordered materials where charge carriers jump between localized states over variable distances, depending on temperature and energy barriers. This hopping process becomes significant at low temperatures, where thermal energy is insufficient to enable conduction through typical band mechanisms. The phenomenon illustrates how defects and impurities in a material can influence the mobility of carriers, ultimately affecting carrier lifetime and diffusion length.

5 Must Know Facts For Your Next Test

1. In Mott variable range hopping, the probability of hopping decreases with increasing distance between localized states, making shorter hops more likely.
2. This conduction mechanism is temperature-dependent, with hopping rates increasing as the temperature rises, allowing for greater charge carrier mobility.
3. Mott variable range hopping can occur in materials with high levels of disorder, such as amorphous semiconductors and certain organic materials.
4. The effective hopping distance is influenced by the density of localized states and the energy difference between these states, which can vary significantly across different materials.
5. Understanding Mott variable range hopping is crucial for designing electronic devices that rely on disordered semiconductors, as it directly impacts their efficiency and performance.

Review Questions

• How does Mott variable range hopping differ from typical band conduction in semiconductors?
  • Mott variable range hopping differs from typical band conduction in that it relies on charge carriers jumping between localized states rather than moving freely through a conduction band. While band conduction involves higher energy levels and less influence from disorder, Mott hopping is significant in disordered systems at low temperatures where traditional conduction mechanisms fail. This understanding highlights how material quality affects overall electrical performance.
• Discuss the factors that affect the hopping distance in Mott variable range hopping and their implications for carrier lifetime.
  • The hopping distance in Mott variable range hopping is influenced by factors such as temperature, the density of localized states, and the energy barriers between these states. As temperature increases, charge carriers gain more thermal energy, enabling them to hop longer distances. This increased mobility can lead to shorter carrier lifetimes if the likelihood of recombination rises as carriers traverse larger distances, impacting device efficiency.
• Evaluate the significance of Mott variable range hopping in the context of developing advanced semiconductor devices.
  • Mott variable range hopping plays a crucial role in the development of advanced semiconductor devices, particularly those using disordered materials like organic semiconductors. Understanding this conduction mechanism allows engineers to design materials that optimize charge transport properties while managing defects. By controlling variables such as localized state density and thermal activation energies, designers can improve carrier lifetime and diffusion length, leading to more efficient devices suited for applications like flexible electronics or photovoltaics.

Related terms

Localized States: Energy states in a material where charge carriers can become trapped due to disorder, leading to non-conductive behavior.

Thermal Activation: The process by which charge carriers gain sufficient thermal energy to overcome energy barriers and move through a material.

Diffusion Length:

The average distance that a charge carrier can move through a material before recombining, influencing device performance.