In semiconductors based devices, defects such as dislocations, grain boundaries, and impurities can function charge traps, which in turn play important roles in determining devices properties
It is always interesting to understand the depth of the charge traps as well as the density. Measuring the thermally stimulated current (TSC) is a good way to investigate this trap related physics.
The procedure of the measurement is to cool down the device to a very low temperature, e.g. 4.2K (liquid Helium temperature) by a cryostat. Then shine light on the device to generate charges until all the traps are filled . Increase temperature to release the trapped charges and read the current vs ramping temperature (Keithley 6430 Sub-Femtoamp Remote SourceMeter can be a good tool). The spectrum can be obtained as similar as the following figure. Each peaks represent a process related to a charge trap. The lower temperature; the shallower trap depth.
Re-plot the Current Vs Temperature at onset of each peak, based on the Arrhenius equation (example as the following figure). From the slope of the plot, the activation energy can be calculated. Thus the density and depth of charges traps can be measured.
Reference: J. Phys. Chem. Lett. 2015, 6, 2350−2354