Are already doped substances used in the process of epitaxy of heterostructures?

Question

Electronics

I became interested in LEDs, in particular, how they work and are created.
As I understood, to create a pn junction, only alloyed substances are needed, but I still did not understand what the active (blocking) layer consists of.
Further, I found out that semiconductors do not solder, as it seemed to me, but build up on each other, and here I can’t get it.
It turns out that if this method is used, then it is not necessary to alloy the substance?
Then how are positive and negative semiconductors held together?
Or is epitaxy and heterostructures another "song"?

Answer 1

"It is not necessary to alloy" - it is not very clear what you mean?
In any case, we need doped semiconductors - one n-type, the other p-type. Those. in any case, "you need to alloy". But a separate technological operation for doping the epitaxial layer may well be absent. The semiconductor is doped directly during the deposition process, i.e. already doped layer grows.

Answer 2

pure silicon is taken and doped with the necessary impurities using ion implantation
methods. The growth of new silicon layers is carried out using gas-phase epitaxy
. Semiconductors were fused a long time ago, at the dawn of semiconductor technology, look for a microalloy transistor.
extension and implantation gives a better result. and quite naturally more subtle elements than soldering / welding :)
google - tyrnet is full of any information.