关键词 > ES2D6
ES2D6 Practical Lab Answer Template – 2024/25
发布时间：2025-03-12
Hello, dear friend, you can consult us at any time if you have any questions, add WeChat: daixieit
ES2D6 Practical Lab Answer Template – 2024/25
1. Abstract* (10 marks total)
Note key conclusions and learnings from the lab.
2. Part A1: Hall Effect Measurement (21 marks total)
A1.1 (1 marks)
Record the sample number.
A1.2 (0 marks)
Having read the instructions, describe any specific experimental methods that you have employed for part A of the lab that were not explicitly given in the lab instructions, including the reasons for doing so. This is so that any experimental anomalies can be taken into consideration during marking.
A1.3.1 (2 marks)
Record the applied series voltage and applied current.
A1.3.2 (1 mark)
Record the precision to which you have set/measured the applied series voltage and applied current (e.g. ±0.02mA).
A1.3.3 (1 mark)
Calculate the conductivity of the sample using equation 4.
A1.3.4 (3 marks)
Measure and record the magnetic field, Hall voltage and the measurement precision for both.
A1.3.5 (1 mark)
Using this information, calculate the Hall coefficient using equation 1.
A1.3.6 (1 mark)
Deduce, from the sign of the Hall coefficient, whether the sample is p-type or n-type.
A1.3.7 (2 marks)
By neglecting the minority charge, calculate charge carrier concentration and mobility.
A1.4 (4 marks)
Reverse the direction of the current flow, setting it to -20mA, and repeat and record all the above steps. Applied current, applied voltage, calculated conductivity, measured magnetic field, measured Hall voltage, calculated hall coefficient, and calculated carrier concentration, calculated mobility.
A1.5* (4 marks, 1 paragraph)
Convert your measurement precision values to percentage uncertainties.
· Combine the uncertainty values from your measured parameters to produce percentage uncertainty values for conductivity, charge carrier concentration and mobility. Show your workings.
· Using only the appropriate uncertainty values associated with the parameters that changed between forward and reverse, say whether any differences between the deduced values for conductivity, charge carrier concentration and mobility between the forward and reverse measurements are significant.
· Comment on the physical factors that might have influenced whether your measurements were the same/different.
3. Part A2: Material Identification (15 marks total)
A2.1.1 (1 mark)
Deduce, from the sign of the Hall coefficient, whether the sample is p-type or n-type.
A2.1.2 (5 marks)
By neglecting the minority charge, calculate charge carrier concentration and mobility. Do this by making a table of Applied current, applied voltage, calculated conductivity, measured magnetic field, measured Hall voltage, calculated Hall coefficient, and calculated carrier concentration, calculated mobility.
A2.2.1 (2 marks)
Use your calculated mobility value to identify what material your sample is made from.
A2.2.2* (3 marks, 1 paragraph)
By considering uncertainties, and random and systematic factors in both the experimental measurement and the material’s structure and physics, comment on why your mobility value might differ from the given values.
A2.3.1 (1 mark)
Rewrite equations 1 and 2 into a single equation (neglecting the minority charge) and extract the constant of proportionality between VH and B.
A2.3.2 (1 mark)
Rewrite equation 5 to give the resistance (NOT resistivity) of the sample.
A2.3.3* (2 marks, 1 paragraph)
By considering the signal-to-noise ratio deduced for both your identified material and the germanium from part 1, comment on which material would make the more sensitive (i.e. highest signal-to-noise ratio) Hall effect magnetic sensor. Initially assume the parameters as used for the given experimental samples and conditions, i.e. fixed material type and doping level; dimensions and applied current. Then discuss changes to sample doping and dimensions and/or current that might be utilised to maximise performance.
4. Part A3: Temperature Dependency (22 marks total)
A3.1 (3 marks)
Calculate the carrier concentration and mobility at each temperature, show the full table of results with Applied current, applied voltage, calculated conductivity, measured magnetic field, measured Hall voltage, calculated Hall coefficient, and calculated carrier concentration, calculated mobility.
A3.2* (2 marks for text answer, 1 paragraph, 3 marks for graph)
Plot Hall voltage as a function of absolute temperature. If a Hall effect magnetic sensor is designed to operate at 30°C, comment on how much temperature variation would be tolerable for a Hall voltage accuracy of ±10%. Repeat your calculation for a sensor designed to operate at 80°C. Show your workings. Annotate this on the graph.
A3.3 (2 marks for numerical answer and comment, 3 marks for graph)
Plot mobility as a function of absolute temperature. At what temperature does the mobility drop by 20% of its room temperature value? Annotate this on the graph.
A3.4.1 (2 marks for numerical answer and comment, 3 marks for graph)
Plot log10 of carrier concentration against 1/(absolute temperature). Observe the intrinsic behaviour at high temperature and the extrinsic behaviour at lower temperature. At what temperature are the contributions from intrinsic and extrinsic carrier generation approximately equal? Annotate this on the graph.
A3.4.2* (2 marks, 1 paragraph)
Recall from lecture 3a how material bandgap influences intrinsic carrier concentration. If samples of germanium (Eg = 0.66 eV) and silicon carbide (Eg = 3.3 eV) were both held at a temperature of 200°C, would they be likely to be dominated by intrinsic or extrinsic behaviour and why?
A3.5* (2 marks, 1 paragraph)
By considering both sensitivity and temperature stability, compare the material identified in part 2 to silicon carbide for the two different applications of jet engine rotor position sensing and non-contact current probe measurements near room temperature.
5. Part B: Diode Current vs. Voltage Measurement (32 marks total)
B1.1* (0 marks)
Having read the instructions, describe any specific experimental methods that you would have employed for part B of the lab that were not explicitly given in the lab instructions, including the reasons for doing so. This is so that any experimental anomalies can be taken into consideration.
B1.2* (16 marks total. 8/16 marks for Graphs. 8/16 marks for a summary table with 1 paragraph)
Plot the results for each diode on a graph showing log10(I) vs. V. Determine the ideality factor in each case at an appropriate value of current density, showing your method. State the current density at which the factor is determined. You will find that the slope is not constant, suggesting a single value of ideality factor will not apply for the whole of any one curve – discuss the reasons why this might be so.
B1.3* (8 marks. 1 page: could contain a combination of 1) calculations, 2) table, 3) graphs, 4) worded paragraph)
The bandgaps of diodes D and F are 1.018 eV and 1.819 eV respectively. From these known values and the measured values of voltage at which your selected current density occurs, estimate the bandgaps of the remaining junctions and suggest which material each might be made from. What are the sources of uncertainty in this analysis?
B1.4* (6 marks, 1 paragraph)
Comment on the agreement between the observed colour of the emitted light from two of the junctions and your conclusion, above, regarding the bandgap.
B1.5* (2 marks, 1 paragraph)
Comment on the applicability of your conclusions to the use of the various types of diodes in different circuits or applications.
