Practical application for germanium sampleby JamesJames Tags: application, germanium, practical, sample 

#1
Mar1105, 10:07 AM

P: 206

I just did a semiconductors experiment involving the Hall effect and a doped germanium sample. The type of doping was determined from the Hall voltage using the sign of the recorded voltage and the sign of the bias current applied across the sample. Now, my question is what could be a practical application of this germanium Hall voltage sample?
I mean where could it be used? How? This is something we are not expected to do in the labs but I am not sure how this could be used in a real life type application. James 



#2
Mar1105, 11:20 AM

Mentor
P: 28,801

Zz. 



#3
Mar1105, 06:30 PM

P: 206

How could it be used to measure the magnetic field strength? I measured the hall voltage and current then got the slope and THEN used this equation to get the Hall coefficient. RH = tR/B where RH is the Hall coefficient, t is the thickness and R is the resistance from the slope of the VI graph. The B field strength was known in my case.
The only way I can see measurement of B is if the Hall coefficient is known apriori. James 



#4
Mar1105, 06:34 PM

Mentor
P: 28,801

Practical application for germanium sampleANY device has to be calibrated. Knowing what the Hall coeff is for your probe is a crucial part of the calibration. So why not? Zz. 



#5
Mar1105, 08:26 PM

P: 206

No no, I mean, are they tabulated for various materials?
James 



#6
Mar1105, 08:27 PM

P: 206

According to that equation above, the B field strength can be obtained only if the HAll coefficient is known...that is why I am asking this question.
James 



#7
Mar1105, 09:07 PM

Sci Advisor
PF Gold
P: 1,457

Yes, they are known. But in all cases, all devices must be calibrated. In any Hall device, both the conductivity mobility and Hall mobility must be measured. From there you can back out the Hall coefficient for that sample. Each sample is different because of doping levels etc....Hall probes are a very common device http://www.lakeshore.com/mag/hlp/hpmm.html
The theory for the hall effect is very straight forward, and using the relaxationtime approximation for the Boltzmann eaquation can yield fairly accurate results to the first order . 



#8
Mar1205, 11:06 AM

Emeritus
Sci Advisor
PF Gold
P: 11,154

JJ,
You might want to think about the point of doing your experiment. What have you gained from it ? The experiment  from your description of it  is not of any intrinsic value to the field, as it has been performed repeatedly in the past (though perhaps not in the specific composition you are working with; but that's likely not very important), so the primary purpose is to teach you certain experimental skills. For instance it might attempt : (i) to show you how a simple Hall measurement yields fundamental information about the nature of the charge carriers; (ii) to teach you how to perform transport measurements in a Hall bar geometry; (iii) to help you gain specific and general experimental skills; (iv) to make you think about how an experiment may be designed to test a theoretical assertion. Also keep in mind that fundamental research need have no foreseeable reallife application. Also, on a side note : von Klitzing won a Nobel prize a couple of decades ago, for doing virtually the same (in theory) experiment you did, on a Silicon MOSFET  he had discovered the Integer Quantum Hall Effect. 


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