MATS 20742 Functional Materials Laboratory Session - 1
PN Junction / Zener Diode / LED Characteristics
Introduction
PN junctions are semiconducting materials with different carrier types (n-type and p-type) contacting
together. They are known as fundamental "building blocks" of most semiconductor electronic devices
such as diodes, transistors, solar cells, LEDs, and integrated circuits; they are the active sites where the
electronic action of the device takes place, thus they play critical roles in modern electronic industry.
This lab study will focus on three typical junction devices: PN junction diode, Zener diode, and LED.
Both forward and reverse bias will be applied onto these three diodes to demonstrate the characteristic
electrical features. Please read the instructions carefully before coming to the lab session, follow the
manuals strictly to carry out the experiments and record data, and finally submit your lab reports before
the deadline.
General instruction:
1. In each lab session, two students will work as a team. So you can choose you own partner, or will
be assigned by the lab demonstrators.
2. Please visually check the equipment, if anything unusual, i.e. broken parts, missing parts, report
to the lab demonstrators.
3. Please read the manual carefully and follow the manual strictly.
4. Before working in forward bias mode (left panel), make sure the potentiometer R2 (right panel) is
at minimum position; Before working in reverse bias mode (right panel), make sure the
potentiometer R1 (left panel) is at minimum position;
5. NEVER touch the wire connections using your bare fingers while device is under operation.
6. NEVER turn on the main power for the system before you have setup all the wire connections,
key switches, and bias switches.
7. For the Zener diode experiment under reverse bias, NEVER apply voltage larger than 4.5 Volts.
8. Power off the system and disconnect all the wires, and put them back to the original position,
before you leave the lab.
9. If there is any issue during the experiments, please ask the lab demonstrators.
Targets:
1. Finish the required three sets of experiments for PN junction, Zener diode, and LED.
2. Record the data of the voltage and current for each set of experiments under both forward and
reverse bias conditions.
3. Plot the I-V curve (can use graph paper or use computer)
4. Summarize the main features for three devices working under both forward and reverse bias
conditions.
5. Based on your lecture study, explain these features using your own words.
6. Finish a lab report based on 2 -5, and submit your lab report at week 25, Mar 16th to the lecturer
and also submit the electronic version in the blackboard.


















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