Magnetoresistance in semiconductor

[Kazza_765]

First off, I'm pretty sure I won't be able to get a definite answer here, just looking for some suggestions. In a physics lab last week, we observed some anomalous effects. First off, let me describe what we did.

We were looking at the Hall effect using SiAs with an As concentration approx. 4*10^18/m^3. Applied a potential difference (6V) across the specimen (4.0mm, 16.0mm, 0.47mm) with an orthoganal magnetic field (0.97 T). The interesting thing occurred as we increased the magnetic field from zero. The current through our circuit decreased by about 7% as we increased the magnetic field from 0 to 0.97 T.

At all magnetic field strengths V=IR still held (R^2 > 0.9999). Since it was not the aim of the prac to investigate this, and we get marked on it, we couldn't spend too much time experimenting. Our demonstrators weren't able to explain it. I'm wondering if this could be due to magnetoresistance or if something else could explain it?

 

[Vailanor]

It's possible that the anomalous behavior could be due to magnetoresistance. Magnetoresistance is a physical phenomenon in which a material's electrical resistance changes when exposed to an external magnetic field. This occurs in certain materials, such as amorphous metals and semiconductors, due to the alignment of the material's magnetic dipoles with the external magnetic field. In the case of your experiment, it's possible that the applied magnetic field caused the SiAs specimen to become magnetoresistive, resulting in the observed decrease in current. Alternatively, it's possible that the anomalous behavior could be due to some kind of surface effect or contact effect. For example, the current path across the surface of the specimen could be affected by the presence of the magnetic field, leading to a decrease in current. It could also be due to some kind of contact effect between the electrodes and the specimen, where the contact resistance increases with increasing magnetic field.Ultimately, it's difficult to say with any certainty what was causing the effect you observed without further investigation. However, based on the information provided, it's possible that the effect was due to either magnetoresistance or a surface/contact effect.

 

[astrokreng]

Thank you for sharing your observations from the lab. It is possible that the anomalous effects you observed could be attributed to magnetoresistance in the semiconductor material. Magnetoresistance is a phenomenon where the electrical resistance of a material changes in the presence of a magnetic field. This effect is commonly seen in materials with high electron mobility, such as semiconductors.

In your experiment, the decrease in current as the magnetic field was increased could be explained by the increase in resistance of the semiconductor material due to the presence of the magnetic field. This is known as negative magnetoresistance. The decrease in current could also be due to the alignment of electron spins in the material, which can cause a decrease in conductivity.

It is also important to consider other factors that could potentially contribute to the observed effects, such as temperature changes or experimental errors. Further investigation and experimentation would be needed to fully understand the cause of the anomalous effects.

Overall, your observations suggest that magnetoresistance may be a possible explanation for the decrease in current with increasing magnetic field. Further research in this area could help to better understand and potentially utilize this phenomenon in various applications.