Pinch off voltage, v
P
The voltage needed to turn “OFF” a JFET. When designing circuits it is essential that the pinch-off voltage be determined to avoid current leakage which can dramatically reduce performance.
Threshold voltage, v
T
The voltage needed to turn “ON” a MOSFET. This is a critical parameter in effective circuit design.
Channel resistance, r
DS
The resistance between the drain and source in the channel. This influences the amount of current being transferred between the two terminals.
Power dissipation, p
D
The power dissipation determines the amount of heat generated by the transistor. This becomes a real problem since the transport properties deteriorate as the channel is heated.
Effective charge carrier mobility, µ
n
The charge carrier mobility determines how quickly the charge carrier can move through the channel. In most cases higher mobility leads to better device performance. The mobility can also be used to gauge the impurity, defect, temperature, and charge carrier concentrations
Transconductance gain, g
m (transfer admittance)
The g
m is a measure of gain or amplification of a current for a given change in gate voltage. This is critical for amplification type electronics.
Equipment needs
- PC with Keithley Interactive Test Environment (KITE) software.
- Semiconductor characterization system (Keithley 4200-SCS or equivalent).
- Probe station.
- Probe tips.
- Protective gloves.
Measurement of (v-i) characteristics
The Semiconductor Characterization System is an automated system that provides both (V-I) and (V-C) characterization of semiconductor devices and test structures. The advanced digital sweep parameter analyzer provides sub-micron characterization with accuracy and speed. This system utilizes the Keithley Interactive Test Environment (KITE) software designed specifically for semiconductor characterization.
Procedure
- Step 1 - Connect the probe tips to the probe station. Then attach the banana plugs from the probe station to the BNC connector, making sure not to connect to ground.
- Step 2 – Select the appropriate connections for your test from
[link] .
- Step 3 – Place your transistor sample on the probe station, but don’t let the probe tips touch the sample to prevent possible electric shock(during power up, the SMU may momentarily output high voltage).
- Step 4 – Turn on power located on the lower right of the front panel. The power up sequence may take up to 2 minutes.
- Step 5 – Start KITE software.
[link] shows the interface window.
- Step 6 – Select the appropriate setup from the Project Tree drop down (top left).
- Step 7 – Match the Definition tab terminal connections to the physical connections of probe tips. If connection is not yet matched you can assign/reassign the terminal connections by using the arrow key next to the instrument selection box that displays a list of possible connections. Select the connection in the instrument selection box that matches the physical connection of the device terminal.
- Step 8 – Set the Force Measure settings for each terminal. Fill in the necessary function parameters such as start, stop, step size, range, and compliance. For typical voltage sweeps you’ll want to force the voltage between the drain and source while measuring the current at the drain. Make sure to conduct several voltage sweeps at various forced gate voltages to aid in the analysis.
- Step 9 – Check the current box/voltage box if you desire the current/voltage to be recorded in the Sheet tab Data worksheet and be available for plotting in the Graph tab.
- Step 10 – Now make contact to your sample with the probe tips
- Step 11 – Run the measurement setup by clicking the green Run arrow on the tool bar located above the Definition tab. Make sure the measuring indicator light at bottom right hand corner of the front panel is lit.
- Step 12 – Save data by clicking on the Sheet tab then selecting the Save As tab. Select the file format and location.
