Why conventional electronics fail in extreme heat

15:02one aspect of that larger conversation. This the potential for this to be an enabling layer is interesting. But before we get into the details of that story, a brief note of housekeeping for our longtime listeners in FFP Nation. Welcome back. If you happen to be catching this episode for the first time, it is the two of us here bringing you the latest breaking science news every week and any way that you can help to support the show so we can combat against the billionaire algorithms. Like, a share, a comment, bring it to Journal Club, put it into the group chat. All of those things help us reach more people with the way in which our

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16:25Nation. But enough of the riff wrath. Let's get back to this very juicy story. I do like my steaks medium rare, [laughter] but I I guess I can make it much quicker if I do it at 700° C. >> Yes. Yeah. It would it would only cook the outside like micron [laughter] >> and then it would be all rare. Um Gordon Ramsay would love that. So, let's first talk about why the conventional electronics that are in our phone, that are in the laptop, everywhere else, why they fail at high temperature. >> Why I can't bring my iPhone and put it in a lava flow. >> Yeah. Yeah. Yeah. I'd like to. >> Yeah, I could put it in water. >> Yeah, but but lava lava is something you

17:06can't do. Okay. [snorts] The physics of high temperature failure. We first have to understand the traditional CMOS architecture that is at the base of all of our technology. This is complimentary metal oxide semiconductor. These devices fail at around 200° C. Here's how it usually works. Okay, so at 0 Kelvin, which means absolute zero, everything is everything is stationary. Silicon is an is a insulator. What ends up happening is atoms have something called a conduction and a veence electron shell. Okay? They've got parts where veence electrons can occupy

17:46all of the shell. So there's nothing going on. All of the shells are occupied, right? Then there's a conduction shell. There's a conduction energy level where there's like one or two electrons hanging out. And those electrons are the ones that skip from one atom to the next to the next and they create current which is what we use. Okay. Now at 0 degrees Kelvin all of silicon's veance band is completely filled. If you put a bunch of metal and a bunch of silicon together the gap between the conduction band and the veance band gets bigger just because of neighboring effects. It's like it's like the the neighboring atoms start pulling

18:28on your own energy gaps and it expands the gap between these two energy bands. >> The wiggle c starts getting more intense. >> Exactly. And so at finite temperature, what you can do is you can bump an electron. You get some wiggle, right? Because like there's jiggling happening. There's photons that are at some energy level that's going to come in, strike an electron. the electron is going to move up to the conduction band and then voila, you can have a little bit of conduction. Okay, now let's get into exactly how this happens. We've got a video that shows exactly how this conduction and veance band works. So on the bottom you've got your silicon. You've got all of the sites that are now

19:08occupied by electrons which are in the >> in the blue. >> It's like the housing market. There's nothing on the market. >> Yeah. Yeah. Yeah. There's no openings. Now all of a sudden somebody sells a house. So an electron from the veence band moves into the conduction band. Now that conduction band electron can move around and create a current. Notice at the same time the hole that was left in the veance band can also move around. It's like you have a bunch of packed theater seats and everybody moves one seat over >> but then the the the empty seat >> can can start moving around too. That's a positive charge in some sense, right? because it's a hole. The electron has

19:49gone away. So, it's left a positive hole. And that hole can move around in the same sense that the electron can also move around because >> because it's attracting because it's that empty space and it needs to be filled and that creates the movement. >> Yeah. The movement, the actual movement, the physical movement that's happening is always electrons, right? It's the negative charge carriers. But the the the the sort of thing that matters in the veance band is that positive hole, >> right, >> that's moving around, right? It it unlocks the stationary state. >> Yeah. >> Uh that exists because it's now moved up to >> Yeah. Yeah. Yeah. Exactly. And so you can have two different types of semiconductors here. You can engineers can make silicon switches using either

20:30phosphorus or boron. You can dope the silicon with either phosphorus or boron. And then these artificially dictate how many charge carriers you're going to get. Are you going to get more electrons in the conduction band? Are you going to get more holes? So that's where you get if you've ever heard of like pt type and n type semiconductors the n type is the negative type semiconductor because the electrons are the ones that are moving around the ptype is the positive type semiconductor because the holes are the one that are moving around and when you combine the two you get things like LEDs transistors but at too high of a temperature you're going to get wrecked. Why? Because if you have too high of a temperature, everything is going to go into the conduction band because there's so much

21:11jiggle and then I'm just going to get a short circuit. It's always going to be conducting. With a transistor, I'd like to control when it's conducting current for a one and when it stops conducting current and becomes an insulator for a zero. But at a high enough temperature, it's always going to be conducting cuz there's so much jiggle that the electrons are just like, "Oh, I'm just going to I'm free to move around. >> Everything moves." Okay? And so part of what we're saying is we're trying to engineer a level of control >> of how this movement happens. And at high temperatures currently in our traditional uh chips and systems, they are unable at high temperatures, you lose the ability to engineer and control the jiggle, the movement, how things

21:51move to the conduction layer and back according. >> Yeah. Yeah. You can't control the transistor going from a one to a zero. It's just always going to be a one. >> Right. Right. Because it's always >> Yeah. And that's the the bedrock of computation. Right. Right. Um now people have managed to make the band gap way bigger because if you make the band gap way bigger then the temperature might not be enough to actually put it up. Right. >> Right. And then and then you can like preserve this transistor property. But and these are authors the authors of the paper that we're talking about they cite this research from NASA research. Um, it shows that you can you can get all the way up to 800 degrees C, but memory is still an issue. Okay, you've created a

22:33sort of circuit element here, digital integrated circuit, but nonvolatile memory, something that retains data even when it's powered down, right? The the stuff that's in our RAM, like I I turn off my computer, it's not like I'm going to lose >> everything >> everything, right? That kind of stuff is still not up to that scale. So through public funding we discovered that it's possible to go above 800. Uh but the the issue still remains memory does not in this context have that high temperature limits. >> Exactly. And if we want to do anything we got to store data right we got to store weights. If we want to do a neural network we got to store what the algorithm is supposed to do. if even if

23:14without the AI stuff, right? If it's just like instructions on what to do, that is stored in your RAM and if the RAM fails, but like your your circuit is doing fine, what's it going to do? There's no instructions. Right. >> Right. Um so most of the applications that we have like in our computer in in the phone, they use something called flash memory. This also uses a transistor. This is the MOSFET transistor. um where you combine a P and an N type and it runs into the same issue with the high temperature because you're using P andN types, right? Um and if even at like a low temperature like room temperature, right, consumer