Building our own iPhone

As some of you might have guessed an iPhone is not what I would build although you can make lots of money with it ... According to some analyses that I found on Caschys Blog the iPhone components cost about 140 EUR and screwing it together makes another 6 EUR. (link) Selling it for a few hundred EUR afterwards earns you quite some cash.

So maybe I would not build an iPhone but I could agree on any other smartphone you can build for 200 EUR and sell it for 600. ;) Starting last week and continuing today and in the next weeks we are basically doing just that in the lab. We are growing transistors. Those are the small magic devices that make your smartphone smart. And your tablet. And your computer. And everything else with electronics. According to Encyclopaedia Britannica transistors are by far the most common human artifact ever produced. (The article is probably not free to view completely - sry! Mabe wikipedia states the same ...) With up to a few billion transistors in every computer CPU this is not hard to believe.

Below there are some pictures we took in the lab with a microscope. You can see two of the main contacts of the transistor. The strucutres are around 20 to 50 µm small. (If you are interested in how a transistor works read below the pictures. :) )

Image 2: Microscope images of transistor structures.

You can clearly see that our smartphone is almost ready. The screwing afterwards is just odds and ends after the transistor growth. ;)






Picture on top: Source (in the middle) and Drain (circle around) contact. The Base contact is still missing and will be added later.

Image 3: Microscope images of transistor structures.

Picture below: Zoomed in. You can see the edges of the structures where they are etched into the photoresist.

If you want to know how a (MOSFET) transistor works here is a short and (hopefully) easy to understand explanation of its basic principle:

Image 3: Schema of a MOSFET transistor.

The green areas in the image to the right contain some charge carriers and the reddish-pink one contains charge carriers of opposing charge. Thus, no current can flow between source and drain if you apply a voltage between them. If you now apply an appropriate voltage at the base contact it will act as one side of a plate capacitor. This will move the charge carriers in the reddish are away from the base and attract carriers of the opposing charge to the base. (There are some few of these in the reddish are as well.) Now there is a so called conduction channel near the base between source and drain. So now a current can flow between source and drain if you apply a voltage here. Maybe you already guessed that this behaviours makes transistors usable as switches. And that is exactly what they are used for in computers, smartphones, tablets, ... (They are all based on binary operations: 0 and 1, off and on - exactly what a simple switch can provide.)