Conclusion
CONCLUSION
The physical properties such as the electronic structure, the electronic and optical features of zinc-blende ScxGa1-xN ternary alloys have been determined and discussed in the frame work of the empirical pseudopotential method disregarding the effect of the compositional disorder. In detail, the direct- and indirect energy band gaps, the antisymmetric gap, the ionicity factor, the effective masses of electron and heavy hole, the refractive index, the static and high-frequency dielectric constants, the transverse effective charge are all addressed.
The major obtained results can be drawn as follows:
Band gap energies
The direct band gap EΓΓ increases non-linearly for composition x varying from 0 to 1. A negative band gap bowing parameter is obtained. A qualitatively similar behavior has been in Ref. [1].
It is noted that on going from x = 0 to 1, the indirect band gap corresponding to the L valley increases up to x=0.5 than it decreases non-linearly. As for the indirect band gap involving the transition in the X valley, it decreases showing a non-linear behavior.
The system transition between the direct and indirect structures occurred at the composition x 0.38 which corresponds to an estimated crossover band gap of about 4.62 eV.
The obtained analytical expressions for EΓΓ , EΓX and EΓL are as follows, EΓΓ
=−3.26x2+4.78x+3.30 EΓX
=−1.59x2+0.68x+4.59 EΓL=−5.37x2+5.53x+6.07
Valence bandwidth
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Conclusion
As a result of an increasing scandium content x on going from 0 up to 1, the valence bandwidth (VBW) is monotonically de-enhanced. Thus, the addition of more scandium atoms in the alloys of interest diminishes the VBW. This might be due to the interaction between the s and p electrons of N with d electrons of the system and the variation of binding energy of valence electrons.
Antisymmetric gap and ionicity factor
The ionicity of a semiconductor is related to the antisymmetric gap. The later is substantially decreased with incorporating more and more Sc atoms in the ternary alloys. This fact suggests that the ionicity character decreases by increasing the Sc.
The iconicity factor decreases non-linearly as the scandium content increases. This can be traced back to the difference in electronegativity between Ga and Sc atoms.
Effective masses
The electron and heavy hole effective masses change nonlinearly with increasing Sc content. These quantities increase with different, but subsequent addition of Sc appears to enhance them very rapidly.
The enhancement of the electron and heavy hole effective masses may decrease the mobility in the material under investigation providing thus less opportunities on transport properties.
Refractive index
Adding some amounts of Sc in ScxGa1–xN diminishes substantially the refractive index on going from x=0 to x=0.5. Above x=0.5 the refractive index is aroused non-linearly.
This is against the general trend common for most of the III–V compound semiconductor alloys [2, 3].
Dielectric constants
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Conclusion
One can note that adding some quantities of Sc in the ScxGa1–xN alloys decreases largely E0 and E∞ . Showing a behavior that is qualitatively similar to that of the refractive index with larger bowing parameter.
Transverse effective charge
It is shown that eT¿ is de-enhanced by increasing Sc content on going from 0 to 1.
Thus higher scandium composition results in a diminution of the transverse effective charge.
The overall obtained results for GaN are in satisfactory accordance with the available data. As for ScxGa1-xN ternary alloys, our results are in general predictions and may serve as a reference regarding the lack of information on this system. Forward work may be focused on elastic, exciton, and polaron properties. Band offsets may also be very useful in heterointerface-based on optoelectronic devices.
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