Photo Dember Effect

The photo dember effect comes from the asymmetric diffusion capability of photoexcited electrons and holes that creates a transient space associated with charge distribution and thereby building up the voltage as well.

Generally, a strong photo dember effect is seen in semiconductors with a huge asymmetry in the electron and hole motion, like in GaAs or InAs. At the same time, it is considered very small in graphene for the electron-hole association symmetry. Here, we will discuss different aspects associated with the photo-dember effect and dember meaning with its application in the field of physics. 

Definition

In the field of semiconductors and physics, the formation of a particular charge dipole in the territory near a semiconductor surface after superfast photogeneration of carriers of charge.

The Dember effect is illustrated as the phenomenon arising when electron current arising from a cathode meant to both illuminations as well as simultaneous electron bombarding is higher than the summation of the photoelectric current and the secondary emission current.

The history behind the photo dember effect

The photo dember effect was discovered by Harry Dember in 1925. The whole effect happens due to two excitations happening by two different electrons, one due to photonic illumination and the other by electron bombardment. In an earlier study made by Dember, he only talked about metals, but later on, more complicated metals were studied for enhanced results.

Application of Photo Dember Effect

One of the major applications of the photo Dember effect is the creation of terahertz (THz) radiation pulses for terahertz time-dependent spectroscopy. This effect is associated with semiconductors, but it is specifically powerful in narrow-gap semiconductors due to their increased electron mobility.

Theory of Photo Dember Effect

Understanding the meaning of dember is important to understand the theory of this effect. It was studied that by means of simulations, the magnitude of the Dember EMF is procured under the semiconductor excitation caused by short laser pulses can be considerably higher than the generic stationary values.

Ultimately, the expression for Dember EMF has presented the support for the explanation of the nature of this particular EMF for the ambipolar diffusion of non-equilibrium electrons and holes as well.

The Dember EMF importantly involves a particular potential difference in the illuminated and dark planes of the sample. Surrounding the two conductors present in equilibrium, a specific contact voltage difference is seen, but it does not create any EMF or current in a closed circuit.

In the explanation of the Dember effect, always open-circuit conditions are studied. For these conditions, the EMF is defined specifically when non-equilibrium carriers are absent and Fermi magnitude for electrons and holes are present.

Such cases happen in the research of thermos-EMF in the existence of a gradient of temperature in the majority of the sample. If the recombination is powerful, the non-equilibrium carriers will distinguish, but the thermo- EMF can still be evaluated in an open circuit. However, in the situation of finite recombination, thermo- EMF is capable of being calculated in any closed circuit.

Unlike the thermos- EMF, the photo- EMF, like Dember EMF, is present only under the influence of a non-equilibrium carrier. In this situation, two different kinds of Fermi quasi levels for electrons and holes are needed, and also, the EMF is not examined by the voltage decrement across the sample. For the calculation, it is important to look into a closed-circuit condition only.

Analysing all the data, it can be said that the conventional approach for calculating the Dember EMF shows a lack of the entire current in the circuit. In the outcome of this approach, the field of exterior forces of non-electrical conditions is spotted with the electric field, which arises for the compensation of diffusion fluxes present in a semiconductor. During the same time, the gradients of the electrochemical potentials are working behind the carriers’ movement within the semiconductor.

What is the Zeeman Effect?

Zeeman effect is the phenomenon or effect where the splitting of a particular spectral line into multiple components in the presence of a particular static magnetic field.

The Zeeman effect is named after the Dutch physicist Pieter Zeeman. He won the nobel prize for this discovery as well.

Conclusion

Summarising what we have discussed above, we can say that the photo Dember effect happens when the electric current coming from a cathode projected to both illuminations as well as a simultaneous electron bombardment is larger than the summation of the photoelectric current and the secondary emission current.

It is highly related to EMF and plays a quintessential role in the field of physics.