I was curious how this worked, so I looked at the paper. My first thought was just about how semiconductors worked in general. You heat something up, you get e

I was curious how this worked, so I looked at the paper. My first thought was just about how semiconductors worked in general. You heat something up, you get electrons in excited states, and this creates pairs of N carriers and P carriers. The N carriers in common semiconductors used in industry have more mobility than P carriers, is that what’s causing the effect? However, when I started thinking more about this idea, it made less and less sense. Turns out there’s a phase change here! The phase change is a reversible phase change alters the crystal structure enough to change between majority N and majority P type carriers. The temperature gradient is necessary to put the N type and P type phases close enough together.