To locate defects dissipating power of 20 mW or less, the test station must heat the DUT by a few degrees. A precisely controlled thermal chuck will do the job, and so will a Peltier device. The Peliter device offers an advantage because it can cool or heat a device. You could also build an inexpensive homemade heater using a variable power supply and a few resistors. Precise temperature control is necessary, but precise temperature measurement is not.
Liquid crystals provide their own temperature indicator.
A high-side switch lets the DUT share a common ground with other power supplies or test equipment. A probing station comprising electrical probes, a thermal stage or chuck, and optical components provides a foundation for testing a semiconductor device using liquid crystals to detect hot spots. A curve tracer lets you set bias conditions so that defects generate heat but do not destroy themselves. Although the test setup requires no other equipment, you might add a video or photographic camera to the microscope to document test results. Some analyses may require more specific operating conditions.