Interest in semiconductor materials had begun as early as 1873 when scientists noticed that the semi-metal selenium actually decreased its resistance when heated. This was most unlike metals. Light was found to have the same effect on selenium.
In world war one, there were massive shortcomings in available communications technology. This lead to whole brigades of soldiers being sent into action without proper coordination. Some physicists served in the signals regiments and were well aware of the communications problems. The development of a proper voice radio naturally became a priority.
Previously, most wireless communication was through crystal radio sets invented in 1906. These radios were unreliable, did not amplify the signal, a large aerial was required to pick up the signal and the transmitting station had to be close. As a result, pressure for the development of a radio which could amplify signals increased. This resulted in the development of the valve wireless, the first amplifying radios capable of driving a speaker. The valves used were triode valves (vacuum tubes with three resistors).
In world war two, it was discovered that valve radios were insufficient in detecting small objects such as the periscopes of submarines. The race was on to build better valves for higher frequency radars that could detect smaller targets. Eventually, scientists discovered that there was a frequency limit beyond which valve devices would not operate efficiently. Microwave radars were developed using silicon crystal mixers. So research into semiconductor materials such as silicon and germanium began in the well-funded Bell telephone laboratories. The first solid-state amplifier, the transistor, was developed in 1948.
Transistors amplified aerial AC signals because they transferred the AC current from a low resistance circuit to a high resistance mains circuit. All transistors until 1960 used germanium as the semi conducting material. Further research into the properties of various materials lead to the germanium being replaced by silicon which was cheaper and better conducting at high temperatures. Scientists also discovered that doping the silicon with other materials such as gallium or arsenic greatly improved silicons conducting abilities. This lead to the development of much smaller transistors which were sketched onto computer chips as part of integrated circuits.
That's my BS...
