The report must have continuous flow without any breaks or abrupt transitions!Everything included in the report must serve a purpose! The report must reflect specifically what you learned in this lab project. Use sections such asIntroduction, Methods, Results and Discussion, and Conclusions.
Microsoft Word - Lab 3 - PN Junction diode.docx EGRE 303 Lab 3: PN Junctions 1 Report due on 10/29/2021, Friday 11:59 pm Exploring PN Junction Diodes Project Goal: In this laboratory project you will explore and understand operation of PN junction diodes and gain insight into limitations of the simplified models using the PN Junction simulation tool available at nanoHUB. (nanohub.org). We have discussed in class the depletion approximation. The depletion approximation is extremely useful, when it is valid, so it is important to understand its limitations. In this work, you will compare the results of depletion approximation analyses of PN junctions with the “exact” solutions obtained by solving the semiconductor equations directly by numerical simulations. The lab will include your calculations of PN junction characteristics based on the depletion approximation and simulations of PN junction diode characteristics using nanoHUB. Access to the simulation tool: For the previous labs, you already registered on nanoHUB. After you login, through resources tab open tools: https://nanohub.org/resources/tools In the central column “Resources” find ABACUS and launch it: https://nanohub.org/resources/abacus You will see the screen below. Select the “PN Junction Lab Original”. By the end of this lab, you should: - Know how to calculate idealized characteristics of PN junction diodes using the depletion approximation - Know how to use nanoHUB PN junction lab to obtain band structure, electric field as a function of applied bias, charge distribution, and IV characteristics of PN junction diodes. - Understand the relation between PN junction design and its forward-bias characteristics, including electric field, charge distribution, and IV characteristics. - Understand limitations of the depletion approximation and relate them to nonidealities in PN junction IV characteristics. EGRE 303 Lab 3: PN Junctions 2 Project Tasks: Part 1: Analytical calculations with the depletion approximation: 1. A Si step junction maintained at room temperature under equilibrium conditions has a p-side doping density of NA = 2 x 1015 cm-3 and an n-side doping of ND = 1015 cm-3. (No “i” region) Use the depletion approximation to compute at equilibrium: a. Vbi b. The depletion layer boundaries, xp, xn, and the depletion width, W c. The electric field at the junction. d. The electrostatic potential at the junction. e. Plot of the charge density, electric field, and electrostatic potential as a function of position f. Plot the ideal I-V characteristics. 2. Repeat Task 1, still using the depletion approximation, but set the p-side doping to NA = 3 x 1017 cm-3 and keep the n-side doping at ND = 1016 cm-3. Compute the same quantities and provide the same plots as in Task 1 and compare results. Part 2: “Exact” numerical simulations and their comparison with the simplified model: 3. In the PN Junction Lab tool on nanoHUB, set the doping densities on the P and N sides of the junction to correspond to those in Task 1. Note that you need to click on the values on the doping graph to change them, Set the length of the P-region to be 1.0 m and the N-region as 2.0 m. Make sure that you have selected “Si” as the material and that the temperature is “300K”. Set the applied voltage to 1 V and minority carrier lifetimes to 1 s. Use sufficient number of steps and nodes to clearly observe the variations. Simulate the defined structure. a. Use the potential vs. position plot to determine the built-in potential of the PN junction. Compare your answer to the depletion approximation result. (Remember that potentials always have an arbitrary reference, potential in the quasi-neutral p-region away from the junction is usually taken as zero.) b. Use the electron and hole density vs. position plots to estimate the width of the depletion layers on the P and N sides, xp and xn. Plot preferably superimposed on top of each other or side-by-side the carrier density vs. position assumed in the depletion approximation and the numerically generated plot, then determine whether the depletion approximation results are reasonable. Explain. HINT: Use appropriate axes for the plot. The vertical and horizontal axes should both be linear with appropriate minimum and maximum limits so that you can resolve the profiles. c. On the electric field vs. position plot, sketch the depletion approximation result and discuss the differences. Do not rely on the depletion approximation plots on nanoHUB, use your own calculated values from Part 1. d. For the net charge density vs. position, plot preferably superimposed on top of each other or side-by-side numerical data and the corresponding depletion approximation result. Again, make sure to use appropriate axes for the plots to resolve the profiles. e. Plot forward-bias IV characteristics obtained from the numerical simulations and compare them with the ideal IV obtained using the depletion approximation. To resolve the details of IV plot, use semi-logarithmic plot, i.e. logarithmic values for the vertical (current) axis. EGRE 303 Lab 3: PN Junctions 3 4. Set NA = 3 x 1017/cm3 and ND = 1016/cm3, and rerun the simulation. a. Compare the depletion approximation results to the simulated built-in potential, Vbi, depletion layer boundaries, xp, xn, depletion width, W, and electric field at the junction. b. On the electric field vs. position plot, superimpose the depletion approximation result and discuss the differences. c. On the carrier density vs. position plot, superimpose the depletion approximation result and discuss the differences. d. On the charge density vs. position plot, superimpose the depletion approximation result and discuss the differences. e. Compare the analytical and numerically simulated IV characteristics. When comparing the numerical and analytical results, copy the numerical results from nanoHUB and sketch/plot the analytical results on the same page for side-by-side comparison. Do not just provide the screenshots of the graphs on nanoHUB. Report Format: Failure to satisfy these requirements will result in a lower grade. 1. Team Report A single lab report must be submitted for the team. The report must have continuous flow without any breaks or abrupt transitions! Everything included in the report must serve a purpose! The report must reflect specifically what you learned in this lab project. Use sections such as Introduction, Methods, Results and Discussion, and Conclusions. Figures (schematics, simulation screenshots, etc.), tables, and equations (e.g. Fig. 1, Table 1, Eqn. 1) must be consecutively numbered in the order they appear and must be properly cited in the text of the report (e.g. as shown in Fig. 2 …, Table 1 tabulates …, According to Eqn. 3 …). All figures and tables must have captions. References must be provided at the end of the document and all references must be cited properly within the text. (Wikipedia is not acceptable) Equal Work Attestation: Reports must include a list of your team members, their individual contributions, and a signature from each member attesting that all members contributed equally to the project. A cover page is not needed; names and the lab title can be provided at the top of the first page of the report. 2. Individual Executive Summary Each team member is required to submit separately an Individual Executive Summary (single page). The executive summary should state the goals in your own words, describe the lab project, summarize the results and important findings, discuss any individual challenges faced and personal learning experience, and reflect what you learned from this lab project. Every student should write the executive summary separately and submit individually. Report Deliverables: 1. Introduction should overview the basics of PN junction devices including major features of their design and typical applications. 2. For Part 1, compile the results of your calculations: a. List the equations used with a legible description of their purpose, specification of parameters, and values of physical constants used (e.g. Boltzmann constant). b. You can use computer software for the calculations if you wish, provided that you list all the equations used as described above. 3. For Part 2, compile all the relevant simulation results: charge density, carrier density, electric field, electrostatic potential as a function of position, and I-V characteristics. EGRE 303 Lab 3: PN Junctions 4 4. In your analysis of the resulting plots, discuss the following. For the symmetrical (or nearly symmetrical) PN junction (where the P and N doping levels are very close), how well does the depletion approximation work? For the asymmetrical PN junction, why does the depletion approximation break down so obviously? Explain using your plots. HINT: To answer this question, it is useful to examine the energy band diagrams, the carrier density plots, and the charge density plot. 5. Discuss deviation of the I-V characteristics from the ideal behavior.