That is likely. Or a hall effect probe. Check it with a diode test function on a meter. If it looks like a diode, attach an 8.2k resistor in series with it and a 9v battery and measure the voltage across it with a DMM on 2v range. Hold the tip between your fingers and see if the value changes on the meter in line with temperature. Or light, try measuring the voltage across it.
I made both of those sensors with old OC transistors as you could scrape the paint off
