ECEA 5722 High-Voltage p-n and Schottky Diodes
2nd course in the Power Semiconductor Devices Specialization
Instructor: Bart Van Zeghbroeck, PhD, Professor
This course is primarily aimed at first year graduate students interested in engineering or science, along with professionals with an interest in power electronics and semiconductor devices . It is the second course in the "Semiconductor Power Device" specialization that focusses on diodes, MOSFETs, and IGBTs but also covers legacy devices (BJTs, Thyristors and TRIACS) as well as state-of-the-art devices such as silicon carbide (SiC) Schottky diodes and MOSFETs as well as Gallium Nitride (GaN) HEMTs. The specialization provides an overview of devices, the physics background needed to understand the device operation, the construction of a device circuit model from a physical device model and a description of the device fabrication technology including packaging.
This second course provides a more detailed description of high-voltage Schottky and p-n diodes, starting with the semiconductor physics background needed to analyze both types of diodes. The main properties of crystalline semiconductors are presented that lead to the calculation of carrier densities and carrier currents, leading to the drift-diffusion model for the semiconductors of interest. Next are a close look at Schottky diodes followed by p-n diodes, with a focus on the key figures of merit including the on-resistance, breakdown voltage and diode capacitance. For each diode, the analysis is then linked to the corresponding SPICE model. Finally, the power diode losses - both on-state losses and switching losses - are examined in a converter circuit, including a comparison of silicon p-n diodes and 4H-SiC Schottky diodes.
Learning Outcomes
Understanding the fundamentals of semiconductors.
Calculating the carrier densities in doped semiconductors versus temperature.
Understanding and calculation of diode breakdown voltage.
Creating a p-n diode SPICE model.
Constructing a Schottky diode SPICE model.
Understanding power diode losses.
Calculation of on-state resistance and breakdown voltage.
Syllabus
In this module, you will learn about semiconductors: the material used to make power semiconductor devices. Specifically you will learn: a) types of semiconductors that are of interest and their crystal structure, b) band structure of relevant semiconductors, c) How to calculate the majority and minority carrier density in a semiconductor, d) How to deal with electron and hole drift and diffusion, and e) How to deal with carrier generation and recombination. This module closes with the drift-diffusion model, the cornerstone of any semiconductor device analysis.
Duration: 6 hours
In this module, you will learn about the simplest semiconductor device, a Schottky diode, which consists of a metal-semiconductor junction. You will apply the drift-diffusion model, solving Gauss' law leading to the depletion layer width, the maximum electric field and capacitance versus voltage relation. Next is the derivation of the Schottky diode current. The analysis of diode breakdown at high voltage is included as well, as is the construction of a SPICE model including parasitic elements.
Duration: 5 hours
In this module, you will learn how to analyze a p-n diode and how it differs from a Schottky diode. Specific items of interest are: a) The capacitance versus voltage relation, b) The diode current, including minority carrier injection under forward bias, c) The minority carrier charge and its effect on switching losses, and d) The construction of a p-n diode SPICE model including parasitic circuit elements.
Duration: 6 hours
In this module, you will learn about the trade-off between diode losses and breakdown voltage including: a) The diode resistance and its relation to the breakdown voltage, b) The switching losses and relation to diode capacitance and minority charge storage, and c) A detailed comparison of SiC Schottky and silicon p-n diodes.
Duration: 3 hours
Duration: 2 hours
Grading
| Assignment | Percentage of Grade |
| Module 1: Semiconductor physics background | |
| Quiz: M1.1 Semiconductor crystals | 1% |
| Quiz: M1.2 Energy bands | 1% |
| Quiz: M1.3 Electron and hole densities | 2% |
| Quiz: M1.4 Carrier transport | 2% |
| Quiz: M1.5 Continuity equation | 1% |
| Quiz: M1.6 Drift-diffusion model | 1% |
| Module 2: Schottky diodes | |
| Quiz: M2.1 Metal-semiconductor junctions | 1% |
| Quiz: M2.2 Electrostatic analysis | 2% |
| Quiz: M2.3 Schottky diode current | 2% |
| Quiz: M2.4 Schottky diode breakdown | 2% |
| Quiz: M2.5 SPICE model of a Schottky diode | 2% |
| Module 3: p-n diodes | |
| Quiz: M3.1 p-n diode structure | 1% |
| Quiz: M3.2 Electrostatic analysis | 2% |
| Quiz: M3.3 p-n diode current | 3% |
| Quiz: M3.4 Minority carrier storage - Diffusion capacitance | 2% |
| Quiz: M3.5 SPICE model of a p-n diode | 2% |
| Module 4: Power diode losses | |
| Quiz: M4.1 Diode resistance versus breakdown voltage | 3% |
| Quiz: M4.2 Switching losses | 3% |
| Quiz: M4.3 Comparison of Schottky and p-n diode power losses | 2% |
| Module 5: Final Exam | |
| Practice exam | 15% |
| Final Exam | 50% |
Letter Grade Rubric
Letter Grade | Minimum Percentage |
| A | 90% |
| A- | 87% |
| B+ | 83% |
| B | 80% |
| B- | 77% |
| C+ | 73% |
| C | 70% |
| C- | 67% |
| D+ | 63% |
| D | 60% |
| F | 0% |
Component List
Reading assignments are provided through Coursera. Suggested reference texts include:
B. Van Zeghbroeck, “Principles of Semiconductor Devices”, http://truenano.com/PSD20
B. G. Streetman and S. Banerjee, "Solid State Electronic Devices”, Fifth Edition, Prentice Hall, 2000.
S. M. Sze, "Physics of Semiconductor Devices”, Second Edition, John Wiley & Sons, 1981.
B. J. Baliga, “Fundamentals of Power Semiconductor Devices”, Second Edition, Springer, 2019.