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Well, every material in column IV of the periodic table (Carbon, Silicon...) is a semiconductor. You basically want to have enough electrons, but not too much.

Well, every material in column IV of the periodic table (Carbon, Silicon...) is a semiconductor. You basically want to have enough electrons, but not too much. Electron density can be adjusted by adding atoms that have too many (column V, on the right), or too few (column III, on the left). Hence III-V semiconductors, like GaAs. You'll notice that Germanium is used as well in some applications (fast, expensive circuits for high frequency applications such as RF). By combining those together, you can obtain a range of properties. I think phosphorus was already used, but the insight here is probably that it is 2D. The way MOS transistors work is that you have a semiconductor that is really just a bad conductor (so it could be made starting from most conductors, "doping" them to conduct less with atoms that trap electrons). By putting an electric field across the semiconductor, electrons will gather together near the positive electrode. Electron density is now enough to meaningfully conduct. So "semiconductor" is just walking a fine line between conducting and not conducting :)

peter_d_sherman 6y ago
>"Well, every material in column IV of the periodic table (Carbon, Silicon...) is a semiconductor. You basically want to have enough electrons, but not too much." Excellent point! While I have your attention, let me advance a "crackpot theory" (Note that this is theoretical only, and completely unproven!): The "crackpot theory" goes something like this: Perhaps every element, not just those on column IV of the periodic table -- is in fact a semiconductor (just that we don't know it currently), but VOLTAGE must vary by element, as must the spacing of entry/exiting conductors -- to get this semiconductor effect in any given element... For metals which conduct normally, VOLTAGE needs to be extremely low, for semiconductors, it needs to be higher, and for apparently non-conducting materials -- much higher still (VOLTAGE will conduct across any material if you make it high enough). You see, VOLTAGE is the original "conductor", regardless of underlying material (the underlying material can just be thought of as a waveguide of sorts). Want a conductor? Raise the voltage high enough for the underlying material. Want a semiconductor? Lower voltage so that the circuit still conducts a little bit of current, and at a certain slightly lesser point stops. Want an insulator? Lower voltage some more until you have one. In any given underlying material, the voltage necessary to accomplish any of these three things will vary, sometimes radically, material to material (i.e., apparent "conductor" to apparent "non-conductor"). Anyway, that's the theory. I haven't been able to prove it or disprove it; it's theoretical only at this point. Also, another key point is that once a substance is electrified, that is, once there is a circuit path established through it (or perhaps around it, if its resistance is higher than air), but once a circuit path is established, the voltage necessary to sustain the circuit from that point forward is usually less than the voltage needed to create it. Simple example: Xenon flash bulb. Xenon gas acts like an insulator to low voltages. It takes a high voltage initial pulse to get it going, but then as it draws current, the voltage to sustain the circuit can be lower. The same with florescent bulbs. Then we have this extremely wierd concept called "ionization". We claim that somehow, if something becomes electrically conductive, it's because of "ions", as opposed to just plain voltage. Well, "just plain voltage" high enough, relative to the resistance of the underlying material -- is what starts the circuit off in the first place... it's a far simpler explanation than 'ions'... Get a Tesla coil, and you'll see that that the high-voltage electricity it produces -- is conducted by so-called non-conductors, even such things as wood... that is, to a tesla coil, wood becomes a conductor, not an insulator... So what is 'doping' then, if there are no ions? Well, think of all materials as memristors of sorts. Running various types of voltage through various types of material in a given direction one time -- changes the breakdown voltage the next time a current-carrying voltage is applied. Now, this effect varies by material, by length, and by amount of voltage applied, and for how long it is applied for. But this "memristor" effect -- would be the equivalent of what today is called "doping" -- if it existed, and I claim (but cannot prove, because experimentation is necessary) that logically, logically, there is evidence to support this (for diodes/transistors, it's called "diode/transistor biasing". Well, "biasing" = "doping" = "applying voltage and then turning it off to change (if ever so slightly) the electrical characteristics of the underlying medium (if ever so slight) for the next time a current-carrying voltage is applied" Anyway, that's the crackpot theory. Voltage. Someone probably discovered that a long time ago and it was forgotten in history as newer trendier concepts were developed... I'm not saying that any of the above theorizing is true; I'm just saying that based on logic, it seems logical... Someone will have to prove or disprove it via experimentation... But, if it's true, then maybe every single element and chemical compound could be used to create transistors in the future -- it's just that at this point in our history, humanity doesn't know how to do this exactly yet... If it's true... If not, well then, "I am a crackpot"... <g>

peter_d_sherman 6y ago

>"Well, every material in column IV of the periodic table (Carbon, Silicon...) is a semiconductor. You basically want to have enough electrons, but not too much." Excellent point! While I have your attention, let me advance a "crackpot theory" (Note that this is theoretical only, and completely unproven!): The "crackpot theory" goes something like this: Perhaps every element, not just those on column IV of the periodic table -- is in fact a semiconductor (just that we don't know it currently), but VOLTAGE must vary by element, as must the spacing of entry/exiting conductors -- to get this semiconductor effect in any given element... For metals which conduct normally, VOLTAGE needs to be extremely low, for semiconductors, it needs to be higher, and for apparently non-conducting materials -- much higher still (VOLTAGE will conduct across any material if you make it high enough). You see, VOLTAGE is the original "conductor", regardless of underlying material (the underlying material can just be thought of as a waveguide of sorts). Want a conductor? Raise the voltage high enough for the underlying material. Want a semiconductor? Lower voltage so that the circuit still conducts a little bit of current, and at a certain slightly lesser point stops. Want an insulator? Lower voltage some more until you have one. In any given underlying material, the voltage necessary to accomplish any of these three things will vary, sometimes radically, material to material (i.e., apparent "conductor" to apparent "non-conductor"). Anyway, that's the theory. I haven't been able to prove it or disprove it; it's theoretical only at this point. Also, another key point is that once a substance is electrified, that is, once there is a circuit path established through it (or perhaps around it, if its resistance is higher than air), but once a circuit path is established, the voltage necessary to sustain the circuit from that point forward is usually less than the voltage needed to create it. Simple example: Xenon flash bulb. Xenon gas acts like an insulator to low voltages. It takes a high voltage initial pulse to get it going, but then as it draws current, the voltage to sustain the circuit can be lower. The same with florescent bulbs. Then we have this extremely wierd concept called "ionization". We claim that somehow, if something becomes electrically conductive, it's because of "ions", as opposed to just plain voltage. Well, "just plain voltage" high enough, relative to the resistance of the underlying material -- is what starts the circuit off in the first place... it's a far simpler explanation than 'ions'... Get a Tesla coil, and you'll see that that the high-voltage electricity it produces -- is conducted by so-called non-conductors, even such things as wood... that is, to a tesla coil, wood becomes a conductor, not an insulator... So what is 'doping' then, if there are no ions? Well, think of all materials as memristors of sorts. Running various types of voltage through various types of material in a given direction one time -- changes the breakdown voltage the next time a current-carrying voltage is applied. Now, this effect varies by material, by length, and by amount of voltage applied, and for how long it is applied for. But this "memristor" effect -- would be the equivalent of what today is called "doping" -- if it existed, and I claim (but cannot prove, because experimentation is necessary) that logically, logically, there is evidence to support this (for diodes/transistors, it's called "diode/transistor biasing". Well, "biasing" = "doping" = "applying voltage and then turning it off to change (if ever so slightly) the electrical characteristics of the underlying medium (if ever so slight) for the next time a current-carrying voltage is applied" Anyway, that's the crackpot theory. Voltage. Someone probably discovered that a long time ago and it was forgotten in history as newer trendier concepts were developed... I'm not saying that any of the above theorizing is true; I'm just saying that based on logic, it seems logical... Someone will have to prove or disprove it via experimentation... But, if it's true, then maybe every single element and chemical compound could be used to create transistors in the future -- it's just that at this point in our history, humanity doesn't know how to do this exactly yet... If it's true... If not, well then, "I am a crackpot"... <g>