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Comment A field full of two layers of firefighters. (Score 1) 105

As mentioned previously, my mental model of semiconductors and the like is a fireman's water brigade, were either the majority of the line has buckets or empty hands.

It helps if, instead of a line, you think of a LOT them standing in a two-D array (like in the yard of the burning building, or a section of a parade that's stopped to do a little demo). It's really three-D, but we'll want to use up/down for something else in a bit...

For metallic electron conduction everybody has TWO buckets, one for each hand, and when a guy by the fire throws a buck of water on it (bucket and all) on the fire, a guy farther back immediately tosses him a bucket, the guy behind him essentially instantly throws HIM a bucket, andso on. Hands are effectively never empty.

For semiconductors, imagine two layers of these guys, the second standing on the firsts' shoulders or on a scaffold right above them, and about enough buckets for each of the guys on the ground to have two and the guys on the scaffold to have none. (There's actually many layers of scaffold, but the rest are so far up that it's hard to get a bucket to them, so they mostly just stand around.)

Usually nothing useful is happening. Everybody on the bottom layer has both hands full of buckets, and it's hard to hand a bucket up to the guys on the top.
  - Electron-hole pair creation: Somebody comes up with the energy to heave a bucket up to the guys on the upper layer, leaving a guy with one hand empty in the lower layer. (Maybe somebody (a photon, for instance) comes along with a lacrosse stick and whacks a bucket up to a guy in the top row - dying or becoming exhausted and much weaker from the effort.) Now you've got one guy with a free hand in the lower layer (a hole) and one bucket on the top layer (a free electron).
  - Electron conduction in a semiconductor is that bucket on the upper layer. The guys there can hand it around easily, or toss it along a diagonal until it would hit a guy - who catches it. They're all standing on accurately-spaced platforms so the bucket can go quite a way before somebody has to catch it. Suppose there's a slope to the yard, with the fire at the bottom. Then, if tossed too far, the bucket might pick up substantial speed and knock the guy who catches it out of place (electromigration), or fall down to the lower layer and knock another bucket out of somebody's hand and bounce, ending up with TWO buckets on the upper layer and an empty hand below (avalanche electron-hole creation).
  - Hole conduction is when you've got an empty hand on the bottom layer: Now it's easy for a guy with two buckets to hand a bucket to a guy with only one, exchanging a bucket for an empty hand. But now the guy whose hand had been empty has two buckets and nobody in the downhill/toward-fire direction to hand a bucket to, while the guy who handed it off has an empty hand and can grab a bucket from somebody farther uphill / closer to the water source - or beside him, or diagonally. So "empty-handedness" (a hole) can move around as a persistent entity while the individual buckets gradually work their way in the general direction of the fire, only making a bit of progress "when a hole comes by". Though the water makes progress toward the fire, the action is all where the holes are making progress away from the fire.
  - Electron-hole annihilation: Somebody has a bucket on the upper layer when a guy below him has an empty hand. So he drops the bucket. CLANG! Ouch! Now there's no "free bucket" on the upper layer, no free hand on the lower layer, and the energy of their separation went somewhere else (knocking the guy sideways so he bumps into his neighbor and generally making the guys vibrate, "creating a guy with a lacrosse stick who runs off to whack at buckets", etc.)
  - P-type doping: A guy in the bottom layer had a sore hand and only brought one bucket to the fire, thus having a free hand from the start. He can take a bucket when a neighbor pushes it at him (the hole moves away). But he'd like to hand it off and have his sore hand free again (so holes tend to stick around at his site). It's lots easier to "make a free hole" by convincing him to hold a bucket in his sore hand than by tossing a bucket up to the guys on the scaffold, but does take a little effort.
  - N-type doping: One of the guys on the upper level really likes to hold a bucket, so he brought one with him. The guy next to him can grab it from him, but if another comes along he'll try to hold on to it a bit until somebody shames him into letting go again or wrestles it from him. It's lots easier to get him to let you use his bucket for a while than to pull one up from the guys on the ground, but it does take a little effort.
  - Tunneling through a potential barrier: There's a ridge across the field. It's hard to hand buckets up to the guys on the ridge, so they don't flow across it very well (unless someone at the side of the field is pushing the buckets really hard...) Occasionally the guys on one side of the ridge hand a bucket through the legs of the guys standing on the ridge to the guys on the other side.
And so on. B-)

I'm keenly interested in finding more material to read up on the observed Hall effect measurements. Thanks again for your contribution to the discussion.

The wikipedia article on the hall effect has a section on the hall effect in semiconductors, but both it and the reference it uses start from treating the hole as a charge carrier with a fixed charge and a mobility different from a free electron, and just computes formulai from there.

If the hall effect on hole currents were fallout from the hall effect on the individual electron bucket-transfers, rather than the hole acting like a positive charge carrier in its own right, you'd think it would go the other way

Comment Another useful vacuum tube: Thermionic converter. (Score 1) 105

Another vacuum tube technology with current applications and substantial advantages over semiconductor approaches to the same problems is the Thermionic Converter. This is a vacuum-tube technology heat engine that turns temperature differences into electric power - by boiling electrons off a hot electrode and collecting them, at a somewhat more negative voltage (like 0.5 to 1 volt), at a cooler electrode.

Semiconductor approaches such as the Peltier Cell tend to be limited in operating temperature due to the materials involved, and lose a major fraction of the available power to non-power-producing heat conduction from the hot to the cold side of the device. Thermionic converters, by contrast are vacuum devices, and inherently insulating (with the heat conducted almost entirely by the working electrons, where it is doing the generation, or parasitic infrared radiation, which can be reflected rater than absorbed at the cold side.) They work very well at temperatures of a couple thousand degrees, a good match to combustion, point-focused solar, and nuclear thermal sources.

Thermionic converters have been the subject to recent improvements, such as graphine electrodes. The power density limitation of space charge has been solved, by using a "control grid" to encourage to charge to move along from the emitter to the collector and magnetic fields to guide it (so it doesn't discharge the control grid and waste the power used to charge it).

Current thermionic technology can convert better than 30% of the available thermal energy to electrical power and achieves power densities in the ballpark of a kilowatt per 100 square cm (i.e. a disk about 4 1/2 inches in diameter). That's a reasonably respectable carnot engine. This makes it very useful for things like topping cycles in steam plants: You run it with the flame against the hot side so it is at the combustion temperature, and the "cold" side at the temperature of the superheated steam for your steam cycle. Rather than wasting the energy of that temperature drop (as you would with a pure steam cycle) you collect about a third of it as electricity.

It also beats the efficiency of currently available solar cell technology (and the 33.4% Shockleyâ"Queisser theoretical limit for single-junction cells), if you don't mind mounting it on a sun-tracker. Not only that, but you can capture the "waste heat" at a useful temperature without substantial impairment to the electrical generation or heat collection, and thus use the same surface area for both generation and solar heating. (Doing this with semiconductor solar cells doesn't work well, because they become far less efficient when running a couple tens of degrees above room temparature.)

Comment Re:Many a young engineer.... (Score 2) 105

... every schematic drawn by every semiconductor engineer got the arrow backwards.

As I heard it, The arrow is "backward" because Benjamin Franklin, when doing his work unifying "vitreous" and "resinous" electricity as surplus and deficit of a single charge carrier (and identifying the "electrical pressure" later named "voltage"), took a guess at which corresponded to a surplus of a movable charge carrier. He had a 50% chance to assign "positive" to the TYPICAL moving charge carrier in the situations being experimented with (charge transfer by friction between different substances, currents in metallic conductors, and high voltage discharges in air and water-in-air aerosols) and happened to guess "wrong".

Thus we say electrons have a negative charge, "classical current" corresponds to the sum of the flow of moving positive charge minus the flow of negative charge (i.e. the negative of the electron current, which is all there is in normal-matter metallic conductors), the arrowhead on diodes (and junction transistors) points in the direction of classical current across a junction, and so on.

But though it's the charge carrier in metallic conduction and (hard) vacuum tubes, the electron ISN'T the only charge carrier. Even in the above list of phenomena, positive ion flow is a substantial part of electrical discharge currents in air - static sparks and lightning. Positive moving charge carriers are substantial contributors to current as you get to other plasma phenomena and technologies - gas-filled "vacuum" tubes (such as thyratons), gas an LIQUID filled "vacuum" tubes (ignatrons), gas discharge lighting, arc lighting, arc welding, prototype nuclear fusion reactors, ...

Move on to electrochemistry and ALL the charge carriers are ions - atoms or molecular groups with an unequal electron and proton count, and thus a net charge - which may be either positive or negative (and you're usually working wit a mix of both).

And then there's semiconductors, where you have both electrons and "holes" participating in metallic conduction. Yes, you can argue that hole propagation is actually electron movement. But holes act like a coherent physical entity in SO many ways that it's easier to treat them as charge carriers in their own right, with their own properties, than to drill down to the electron hops that underlie them. For starters, they're the only entity in "hole current" that maintains a long-term association with the movement of a bit of charge - any given electron is only involved in a single hop, while the hole exists from its creation (by an electron being ejected from a place in the semiconductor that an electron should be, by doping or excitation, leaving a hole) to their destruction (by a free electron falling into them and releasing the energy of electron-hole-pair separation). They move around - like a charge carrier with a very short (like usually just to the next atom of the solid material) mean free path.

For me the big tell is that they participate in the Hall Effect just as if they were a positive charge carrier being deflected by a magnetic field. The hall voltage tells you the difference between the fraction of the current carried by electrons excited into a conduction band and that carried by holes - whether you think of them as actual moving positive charge carriers or a coordinated hopping phenomenon among electrons that are still in a lower energy state. Further, much of interesting semiconductor behavior is mediated by whether electrons or holes are the "majority carrier" in a given region - exactly what the hall effect tells you about it.

So, as with many engineering phenomena, the sign for charge and current is arbitrary, and there are both real and virtual current carriers with positive charge. Saying "they got it wrong" when classical current is the reverse of electron current is just metallic/thermionic conduction chauvinism. B

Comment Re:Vacuum tubes handle EMP's better (Score 1) 105

"No point progressing since the bombs are gonna fall any day now. Then where will your fancy silicon highways and databases be?"

Given that the Internet Protocol and much of the rest of the networking technology that still underpins the Internet were developed as part of a cold-war program to create a communication system that could survive a nuclear attack that destroyed most of it, and still reorganize itself to pass messages quickly, efficiently, and automatically among any nodes that still had SOME path between them, your post seems to come from some alternate universe to the one I inhabit.

Comment Re:I'll believe it when I see it (Score 1) 50

And yet for all your misdirected Windows whining DirectX for Windows is the only area that AMD cards perform well. Their Linux drivers blow, as noted by other posts here, and that is because AMD can't write OpenGL drivers to save their life.

nVidia, on the other hand, has extremely fast and solid drivers for Linux.

Comment Well of course, because Linux is OpenGL (Score 1) 50

And AMD can't handle OpenGL. I don't know why, I'm not sure what's so hard, I'm not sure if there's a monster that guards the OpenGL specs in the AMD office or something, but they have sucked at GL for over a decade, and show no signs of getting any better. They can't claim it is because of an API limitation either. For whatever you want to say about the mess that is OpenGL, nVidia makes their GL drivers dead even with their DX drivers. You can use either rendering path and can't tell the difference in features or speed.

That is also why I'm real skeptical that Vulkan is going to do anything for AMD. While they are heavily involved in the development, they are involved with OpenGL's development too (ATi was a voting member on the ARB and is a promoter with Khronos Group). Given that Vulkan is heavily GL based, originally being named glNext, I worry that AMD will suck at performance with it as well.

Comment I'll believe it when I see it (Score 2, Insightful) 50

Not the driver, that's out, but that they are going to change how they do drivers. They've said that numerous times before, and always the situation is the same. They are very slow at getting actual release drivers out (they are forever beta versions) and their OpenGL performance and support is garbage (to the point that HFSS would fail to run on systems with AMD cards).

So AMD: Less talk, more good drivers. I want to support you, I really do, but I've been burned too many times.

Comment And what does that cost for gigabit routing? (Score 1) 111

The problem PFSense has as compared to consumer routers is that running on normal Intel CPUs it needs more CPU power (and thus cost) to be able to forward a given amount of traffic. Plus all the NICs and such are separate silicon. Boradcom makes little all-in-one chips that have a couple of ARM cores that have acceleration for routing and so on. Also they have things like an ethernet switch and ethernet PHYs on the chip so they needn't be added. Have a look at a BCM4709A for an example that is popular in routers.

PFSense is good but it is not the most economical thing if you are talking features matching a consumer router, meaning gig routing, multiple ports, and wifi, you can have your costs go up a fair bit. Particularly if you also then want it to be fairly small and low power. If you hop over to PFSense's site it would cost about $575 for a SG-2440 with WiFi which would give features roughly on par with a consumer router.

While I'd much rather have that over a consumer router, a consumer router is in fact what I have because I didn't want to spend a ton of money for a home router.

Comment Re: Live by the sword, die by the sword. (Score 4, Insightful) 251

Oh look, someone broke into your house, and stole all your valuables and personal belongings. Well you were stupid enough not to use bank vault doors, and you gave the spare key to a close friend who didn't lock his door that day.

The problem with Information security is that to be safe you need professional level of security on your consumer devices, and constant vigilance to keep it up. This is a lot of work for a person, especially if they don't find security patches fun, or barely get by using the internet.

Comment Re:Live by the sword, die by the sword. (Score 4, Insightful) 251

So we should be all nice and fuzzy with a group intent of harassing people. Oh they are making peoples lives miserable, but let them just go on their marry way, because if we mess with them they will mess with us too.

Yea it is OK the Nazi were capturing Jews, because we weren't Jews, if we did try to stop them, then they would just go after us.
Yep that mentality is looked soooo fondly in the view of history.

Comment Re: OMFG! (Score 3, Interesting) 174

No I am saying different genders will gravitate towards different jobs. Towing more women at a job to meet a quota even if that isn't what they want to do, will just cause a higher level of turn over. However as I stated before this is a trend, not a rule. Like any trend there are exceptions... A lot of one, a Trend can mean 51% of a population will fall in such a category (assuming I have a low margin of error) meaning 49% will fall in the minority. 49% is a big minority.

There are a lot of talented women who are just as good if not better then men at the building and creating of technology, if that is what they want to do, we shouldn't say they can't because of their gender. However if there is a balance in the stereotypes and you find your organization isn't having the gender equity, then there is a problem with the organization which will need to be corrected, such as fostering values that will attract women stereotype tech workers to your field, as they will bring something the organization needs anyways.

Comment Re:OMFG! (Score 1) 174

I work in a division where the gender population across the tech folks is 50/50 There is still an open position so depending who we fill in that roll will make the determining factor. However I work in health care, that industry will naturally attract a higher female group.
However in terms of looking at rolls to fill and the people who apply I find the following trends.
Male Tech workers: Focus a lot on the technology, they like to build and create, when there is a problem they will jump in and tackle it. When there is a development job they will be the first to volunteer.
Female Tech workers: Focus on the people, they are more likely to dig into a problem and find where it went wrong, offer suggestions on how to make a product better, and work with others to find what the ideal solution would be.

Working in a hospital we need a good mix of both, however if you are working in a place that builds software far more men will be attracted to that type of work.