Grown Diffused
Grown Diffused Transistor
For the full history of Texas Instruments on this site please return to The Early History of Texas Instruments Semiconductors.
The grown diffused process was developed by Texas Instruments in order to make transistors that could operate at radio frequencies needed to make the first portable transistor radio: the Regency TR-1
The initial melt doping is controlled for the desired collector conductivity and the collector is grown. Base and emitter dopants are added simultaneously. During the growth of the emitter region the base impurities diffuse into the collector region creating a narrow base. The method is restricted to PNP germanium transistors and NPN silicon transistors. This is because in germanium donors (N) diffuse more rapidly into the collector forming the base and in silicon the reverse is the case.
Grown diffused transistors have an internal electric field due to an impurity gradient through the base layer: a natural outcome of diffusing in the base impurity from the emitter side only. The potential was first recognised by Kroemer, who called this structure the drift transistor. The field accelerates the carriers through the base and the faster transit time improves the frequency response of the transistor. [Cornelison 1957 Kroemer 2001]
Cornelison B Adcock W Transistors by Grown-Diffused Technique Proc 1957 IRE WESCON Convention Record Part 3 22-7
Kroemer H 2001 Quasi-Electric Fields and band Offsets: teaching Electrons New Tricks Rev Mod Phys 73 783 - 93