What is Si-delta doping? I want to know what the delta means in this case.
I know the Si means the element used, by some way to doping.
I guess the delta means that using some elements to create holes in semiconductor made of Si.
Am I right?
 A: Delta-Doping is a technique, usually used in MOCVD growth, which can be used to get thin layers of high dopant concentration or, if combined with annealing, to get homogeneous doping with very high dopant concentration.
The usual delta-doping procedure consists of multiple growth steps, where the host material and dopant sources are opened intermittently. Some authors also leave the host material source open all the time and just open/close the dopant source. By this, relatively thick nominally undoped layers are interrupted by relatively thin layers with very high dopant concentration. 
A use case is high concentration p-type doping of GaN. 
See for instance: C. Simbrunner et al., Appl. Phys. Lett. 90, 142108 (2007)
A: Similar to soulsource's answer, I think what you are referring to are 
Silicon devices (ie. Silicon substrate, like a CMOS chip), in which some layer has very high dopant concentration.  This could either be a p- or n- type dopant - which determines the element that one would dope with (eg. B for p-type Si, and P for n-Si).
Delta-doping is often used in Tunnel Junctions, for example in GaAs & InP-based photonic devices.  GaAs can be delta-doped n-type with Silicon - it's possible that the "Si-delta doping" you're referring to may be referring to this.
I would think that the "delta" refers to a doping profile that looks like a delta function - ie. a sharp spike in the amount of doping at a particular depth, and very little high doping in the adjacent layers.
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Some refs:


*

*Delta doping in Silicon: Growth of delta-doped silicon layers

*Si-delta doping for GaAs tunnel junction: Application of δ-doping in
GaAs tunnel junctions
A: Generally one dopes a semiconductor, which has a certain intrinsic charge carrier concentration contributing to its conductivity, by another material (impurity of the crystal structure of the solid state material by foreign atoms) to increase this electrical conductivity. But to be able to answer more precise, it would help to give a formula in which the $\delta$ occurs. Depending on whether electron themselves are mainly responsible for electric currents or electron gaps (holes), which act as positive charge carriers, one conventionally speaks of a $n$-or $p$-doped semiconductor respectively.
