Undoped semiconductor shows better crystallinity in terms of higher photoluminescence (PL) intensity, in comparison to gallium doped semiconductor.
But SEM images show that undoped semiconductor has defects and gallium doped semiconductor has less defects. How to explain it in terms of crystallinity? Whose crystallinity better in between undoped and doped semiconductor?
Doping a material at high temperature will produce in it crystallographic defects. But this crystallographic defects may have some gettering action on the harmful crystallographic defects which may act as nonradiative recombination centers.
In order to get out the density of the recombination centers you can measure the
the minority carrier lifetime. The minority carrier lifetime is inversely proportional to the density of the recombination centers. Also the passivation of the surface due to doping may cause also lower surface recombination rate and overall smaller recombination rate.
Best wishes
Please read thsi paper
Article Effect of Ni doping on electrical, photoluminescence and mag...
It is obvious that doping reduces the crystallinity of any semiconductor material due to defects as compared to intrinsic material. But how you have detect defects from SEM images? Please share the SEM pic. Defect may comes from the grain boundaries or from the cracks of the material.
SEM/TEM results in general show the properties of a very limited amount of sample, but the average property might vary significantly. Hence, in my view, you should further characterize your sample to be sure of the doping-effect on crystallinity. But, generally doping has a negative impact on crystallinity, and increases cracks/defects (at interfaces and point-defects) and associated microstrain.
I'd recommend further analysis: (i) Williamson-Hall analysis of XRD, (ii) BET analysis, (iii) Repetition of SEM/TEM, (iv) and if possible first principles (DFT) calculations can be done to understand the effect of that dopant on your material, (v) Prepare more samples with different doping percentage to verify the trend.
Dear paramita SEM will be used to detect suface morphology . but , not to find doping changes and you can't do that. It can be proved b y change in impedance but not SEM figures.
How was it doped and what level of doping? Ion implantation or MBE? Was it annealed before SEM? Any intentional or unintentional thermal or optical annealing can reduce the doping related defects. Therefore, it is possible that doped SEM look more crystalline after doping
There is no direct connection between PL efficiency and crystallinity. PL efficiency depends on the competition between radiative and non-radiative processes. Some times impurities or some sort of disordering can actually improve PL efficiency. I am not familiar with the specific material in question. See some general discussions about PL efficiency in this paper:
Article Comparative studies of optoelectrical properties of prominen...
Doping a material at high temperature will produce in it crystallographic defects. But this crystallographic defects may have some gettering action on the harmful crystallographic defects which may act as nonradiative recombination centers.
In order to get out the density of the recombination centers you can measure the
the minority carrier lifetime. The minority carrier lifetime is inversely proportional to the density of the recombination centers. Also the passivation of the surface due to doping may cause also lower surface recombination rate and overall smaller recombination rate.
Best wishes
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