Design of Power Semiconductor Devices, ES4E8 assignment, 2023/24
Module Code |
ES4E8 |
Module Title |
Advanced Power Electronic Converters and Devices |
Assignment Title |
Design of Power Semiconductor Devices |
Assignment Weighting / Credits |
30% coursework / 4.5 CATS |
Submission Deadline |
Noon Thursday Week 21 (22nd February 2024) |
Intended Learning Outcomes (ILOs) Assessed
Intended Learning Outcome(s) (ILOs) |
Task / Criterion / Section |
LO1: Apply advanced concepts through the use of device physics in the context of device design. [M1, M2, M3, M4, M6] |
In this assignment, there are three questions. Please answer all questions. Question A [M1, M2, M3, M4, M6] Question B [M1, M3, M4] Question C [M1, M2, M4, M6] |
Notes:
• A total mark below 40% indicates that the ILOs have not all been met at threshold level;
• A total mark in the range 40 - 48% indicates that the ILOs have all been partially met to at least threshold level;
• A total mark of at least 50% indicates that the ILOs have all been met.
Submission Details
The submission details for this assignment are:
• Deadline: 12 noon Thu 13 th February 2025.
• Method: Online submission via Tabula.
• Format of submission: A single .pdf file with a meaningful filename that would contain the student number, the module code, and assignment name, for example:
“1234567_ES4E8_Lab Report.pdf”
• Submission length: Maximum 2000 words. You will lose 5 marks per extra page over the limit.
• Formatting instructions: Use a minimum 11-point Arial (or equivalent) font for the text, with 1.5 line spacing and 25 mm margins all round.
Note: Submissions should be of an appropriate file size and students are responsible for ensuring that work is uploaded successfully before the deadline. If there are technical issues when submitting online, please contact the Engineering Student Office (eng.eso@warwick.ac.uk).
Guidance and Referencing Style
It is serious Academic Misconduct to pass off the work of others (including peersor AI-based chatbots such as ChatGPT) as your own and you should not permit colleagues to copy from you. Sources must be appropriately and properly acknowledged everytime reference is made to another’s work, using the Harvard Referencing system. Failure to do so amounts to plagiarism which breaches university regulations and falls short of the Academic Integrity expected in the department and university.
Find out more about the School of Engineering Referencing System here:
https://warwick.ac.uk/fac/sci/eng/eso/undergraduate_students/guidance/handbook/skills/s hb-2-04
There are also other types of academic offences including duplication or ‘self-plagiarism’ . Refer to https://warwick.ac.uk/fac/arts/history/students/undergraduate/assess-plagiarism/ for further details.
Style. and Formatting Guide
Submissions are expected to conform. to professional standards on style and formatting, and guidance can be found here:
https://warwick.ac.uk/fac/sci/eng/eso/undergraduate_students/guidance/handbook/skills/s h-1-06/
Assignment Feedback
• Your submitted report will be marked electronically. The marks of the various
sections will be provided as well as an outline of the answers of the various sections in order to identify where/how to improve.
Question A
A= (last two digits of your university ID number+450)
B= (last two digits of your university ID number×7+1000)
1. Figure 1.1 shows the basic cell structure of a power MOSFET.
Describe the internal resistance components in the power MOSFET on-state operation as shown in
figure 1.2(a) and (b) and comment on their effect as the device voltage rating increases. [5%]
Figure 1.1. Lateral channel power MOSFET - device parameters.
Figure 1.2 (a) Planar power MOSFET and (b) Trench power MOSFET.
Table 1: Device parameters
2. Calculate the on-state resistance % contribution at room temperature of each internal resistance component over the total on-state resistance for a “A”V breakdown rated MOSFET @ Vgate=15V, Vthreshold= 6.4V and Vdrain=0.6V (where the value of “A” is defined above). Identify the most important resistance contributions.
Use the device parameters as given in table 1 (you may find reference [1], section 6.4 & 6.5 useful for this analysis). [10%]
3. Calculate the on-state resistance % contribution at room temperature of each internal resistance component over the total on-state resistance for a “B”V breakdown rated MOSFET @ Vgate=15V, Vthreshold= 6.4V and Vdrain=0.6V (where the value of “B” is defined above). Identify the most important resistance contributions and discuss how these compare to your finding in part (3).
Use the device parameters as given in table 1 (you may find reference [1], section 6.4 & 6.5 useful for this analysis). [5%]
4. Using MATLAB (or analogous software) discuss how the variation of JFET region LJFET (i.e the distance between the two p-base regions LJFET= 2*LA) affects the performance of the device in part
(2) with specific reference to internal resistance components. Keep the cell width and channel length constant. Illustrate your answers by means of corresponding plots. [5%]
5. Discuss how a 1.2kV breakdown-rated Silicon MOSFET device would alter the on-state resistance contributions as the temperature increases from room temperature to 125C° . [5%]
6. Discuss how the on-state and off-state performance differs between the Trench MOSFET and the
Planar MOSFET. Refer to Figures 1.2 (a) and (b) for comparison. [5%]
References
[1] Book “Fundamental of Power semiconductor Devices” B.J. Baliga, Springer International Publishing 2008.
Question B
The unipolar limit is the theoretical maximum current-carrying capability of a unipolar semiconductor device, such as a MOSFET, where only one type of charge carrier (either electrons or holes) contributes to conduction. This is usually represented as the relationship between the breakdown voltage vs the specific on-state resistance. The unipolar limit for Silicon is plotted in Fig.2.
An abrupt one-dimensional P+N diode is described by the following equations for the maximum electric field (EM ) V/cm at the junction and the thickness of the depletion region (WD ) cm, as functions of the doping concentration (N) cm-3 and the applied reverse bias voltage (VR ):
Critical electric field (Ec) for Si, SiC and GaN materials is shown below:
Electron (μe) and hole (μℎ) mobility models for Si, SiC and GaN are shown below:
References
[1] Book “Fundamental of Power semiconductor Devices” B.J. Baliga, Springer International Publishing 2008.
[2] T. Hatakeyama, K. Fukuda and H. Okumura, "Physical Models for SiC and Their Application to Device Simulations of SiC Insulated-Gate Bipolar Transistors," in IEEE Transactions on Electron Devices, vol. 60, no. 2, pp. 613-621, Feb. 2013, doi: 10.1109/TED.2012.2226590.
[3] T. T. Mnatsakanov, M. E. Levinshtein, L. I. Pomortseva, S. N. Yurkov, G. S. Simin, and M. A. Khan, "Carrier mobility model for GaN," Solid-State Electronics, vol. 47, no. 1, pp. 111–115, 2003, doi: 10.1016/S0038-1101(02)00256-3.
[4] J. A. Cooper and D. T. Morisette, "Performance Limits of Vertical Unipolar Power Devices in GaN and 4H-SiC," in IEEE Electron Device Letters, vol. 41, no. 6, pp. 892-895, June 2020, doi: 10.1109/LED.2020.2987282.
Given the theory above:
1. Derive and plot the unipolar limit (breakdown voltage vs specific on-state resistance) for all three materials: Si, SiC and GaN, where the majority carrier is electrons. Clearly state equations used to plot the unipolar limit and discuss the fundamental differences between those materials. Note, that the breakdown voltage range should be within 100-10 000 V range. [10%]
2. Using the mobility equations provided above, plot the mobility vs doping for p-type and n- type Si, SiC and GaN materials and discuss the differences between p-type and n-type Si, SiC and GaN materials in the context of their impact on power device performance [10%].
3. Three semiconductor manufacturers, A, B, and C, fabricate 650 V Si MOSFET devices. The performance of these devices is reported in Fig. 2. Explain the difference between the performance of the device C compared to A and B. [10%]
Figure 2 Performance comparison of MOSFET devices from manufacturers A, B, and C.
Question C
Figure 3.1 shows the on-state characteristics of a 3.3kV Si and SiC PIN diodes at 25°C. Parameters of which are summarized in Table 2.
Table 2. Parameters for 3.3 kV Si and SiC PiN Diodes.
The 3.3 kV SiC Schottky diode has the following I-V equation:
Where A∗ is the Richardson’s constant equal to 146 A.cm-2K-2 and ΦBN (eV) is the barrier height.
1. Discuss which type of diode you would use for applications of 100 A/mm2. (10%)
2. Justify the differences of the two curves given the material properties (i.e. Vo value and differential resistance (line curvature))? (15%)
3. Identify the SiC Schottky diode forward voltage drop at 100 A/cm2 and plot the I-V characteristics for the Schottky contact metals with ΦBN equal to 0.6 eV, 1.0 eV and 1.5 eV. Discuss how the selection of the contact metal will affect the on-state and off-state performance. (15%)
Figure 3.1: The on-state characteristics of a 3.3kV Silicon and Silicon Carbide PIN diodes at 25°C
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