Essentially electrons in crystalline materials (which GaN and Si are) behave "quantumly". This can lead to weird effects such as an electron appearing to be heavier or lighter than you would expect depending on the material. Another property is the speed at which the average electron appears to be moving (drift velocity) when a given electric field (E) is applied. Mobility is simply dv/dE which ideally is linear (isn't the case at high E). The crystallinity of a material is important to this value. Graphite and carbon are both allotropes of carbon yet have different mobilities.

GaN seems to have a higher electron mobility than silicon (~10,000 vs 1,200 cm^2/Vs for undoped GaN and Si respectively). This is only a 10x difference so I'm not quite sure where they get the 1000 figure. If you take a piece of GaN and apply 1V 1 cm apart the electrons would move at 10k cm/s while in silicon would only move 1.2k cm/s. Faster electrons allow you to shrink transistors and achieve the same current. For example faster water flow allows you to use a smaller hose to deliver water to the destination at the same rate.

As someone who has worked in high tech manufacturing in Europe, the US, and Asia this is absolutely true. As an American and representative of a American company my experience was that once we had arduously hashed out the detailed specs and reached an agreement with our European supplier we could be confident they would not try to deliberately sneak anything past us. My experience with an Asian supplier was the opposite. I experienced outright lying on compliance matters and no apology or sense of fault when I had hard evidence to prove my case. It was a case of constant suspicion and need of monitoring. I much preferred working with the Europeans. While we certainly had our differences and heated disagreements, once an agreement was reached it was adhered to. Business-wise it was so much more refreshing to explicitly confront disagreements at the get go before the ink was dry rather than worry about being told yes (our Asian customers always answered yes to every question even when they had no intention of carrying it out) and finding your agreement was actively being undermined.

The 4004 is VLSI? I don't think it means what you think it means...

I work in the semiconductor industry. I don't deal with memory, I deal with ASIC chips but I can absolutely assure you that the current situation in the semiconductor business is exactly as described. Picture this, you are a manager in a semiconductor company approximately one year ago. You are facing an unprecidented once-in-a-lifetime global economic downturn. You can feel it. The press feels it and reports on it non-stop. Nobody knows when the world will pull out of it but it is obvious to everyone that it hasn't ever, in anyone's lifetime, "been this bad". You know, as a semi company manager, that you have *tremendous* capitol costs (a new factory costs in the billions). What are you going to to? Continue to invest billions in capitol for factory expansion and improvement in the face of unprecedented plummeting demand? Your company's billions are already evaporating in the economy. If you keep spending as you were you would quickly exhaust your company's finances and in addition cause a glut in the global supply of chips (where demand is shrinking) driving down prices like a rock. No, you do what every other company in every other productive sector of the economy does. Cut back production to match demand. The thing is, you can't quickly turn the huge ship of semiconductor production. I'm sure you'll find that semiconductor capacity *always* lags demand. I'm sure in the downturn there was a glut as they realized and as quickly as they could (albeit relatively slowly) responded to market conditions. I can assure you that right now we have the problem that we can not produce enough parts. We are leaving money on the table in the form of unfulfilled demand at the moment. Is that ideal? No, better than the alternative but still a problem. Is there collusion in the industry? Hell if I know but in sum, take it from an industry insider that the factors mentioned in the article are absolutely real and more pronounced than they have ever been in my career.

Well, I do look at photomask stacks as part of my job from time to time as a process integration engineer (mask bugs do make it past design rule checking and tapeout sometimes) but I will start with a disclaimer that this chip and process was designed before I was alive.

It looks from the composite drawing that this is a single poly/single metal/self aligned doped poly/source/drain. That should have existed at the time and to my knowledge no metal gate process has been in wide use because of manufacturability and performance problems. It looks like the red is poly (gates and lines), blue metal, and the green is the source/drain/poly doping diffusion. Whether that was done with implantation or glass doping I'm not sure (again before my time, implant was coming into use but glass doping was much cheaper, if not as controllable). It is kind of nice to see such a simple design.