pn Junction Diodes

The pn Junction Diodes are tested in the lab using ICS, an automated testing program. For more information, see Testing.

Reverse Breakdown Voltage

Theory

Diode geometry and doping affect the reverse breakdown voltage of the diode. The higher fields created in corners will cause breakdown to occur in the corners. The corners result from lateral or vertical geometry. Higher fields are also created by higher doping concentrations.

Measurement

Determine the reverse breakdown and turn-on voltages for the round, square, and finger diffusion #1 and #2 diodes. From top to bottom in the above figure are the diffusion #1 diodes, diffusion #2 diodes, and Schotty barrier devices. The Schottky barriers will not be used in this section. Remember to record the method used to determine reverse breakdown voltage (line fit and extrapolation, or current of -1 mA, etc.)

Questions

1. Which diode had the smallest absolute reverse breakdown voltage? Why? Is it the one you expected?

Optical Effects

Theory

There are two round diffusion #1 and diffusion #2 diodes. They are approximately the same size, but one diode is not covered by the aluminum contact. Optical injection will affect the reverse leakage current.

As photons hit the silicon, they will create electron-hole pairs which will drift in the field to produce current. The intensity of light should be proportional to the number of electron-hole pairs created and the current.

Measurement

Measure the reverse leakage current for the exposed diode with the light on, then with the light off. Be sure to close the cover for the dark measurement.

Make sure that you use the same voltage reference for each reverse leakage current measurement.

Note whether the light affects the sharpness of the reverse breakdown. You may make measurements at different light intensity settings, and note the dependence of reverse leakage current on the light intensity.

Questions

1. Does the light affect the reverse leakage current of the diode?
2. Do the positions on the light power supply appear to be linear, logarithmic, or neither? (Use your leakage currents to answer.)

For Additional Information Consult:

1. Arthur B. Glaser and Gerald E. Subak-Sharpe, Integrated Circuit Engineering, (Addison-Wesley, Reading, MA, 1979), pp. 24-26.
2. Ben G. Streetman, Solid State Electronic Devices, (Prentice-Hall, Englewood Cliffs, NJ, 1980), pp. 162-166.
3. S. M. Sze and G. Gibbons, "Effect of Junction Curvature on Breakdown Voltages in Semiconductors," Solid State Electronics, 9, p. 831, (1966)