The effect of N-vacancy and In aggregation on the properties of InAlN

Abstract

In 0.17 Al 0.83 N, lattice matched to GaN, is an attractive solution for applications such as high electron mobility transistors, distributed Bragg reflectors, or light-emitting diodes. It has been reported that InAlN layers lattice matched to GaN on growth along the [0001] exhibit crystallographic degradation when the thickness is increased. In our recent work, it was shown, through theoretical modelling as well as transmission electron microscopy, that the N vacancy (V N) plays a critical role in this behavior. In this work, we have carried out a detailed theoretical investigation of the possible modification of the properties of this alloy as brought about by the presence of the nitrogen vacancy and the associated formation of the indium rich regions. After testing the ab initio procedures on the AlN and reproducing the lattice parameters and band gap with high accuracy, it is shown that the indium aggregation in InAlN leads to a reduction of the band gap. In contrast to AlN, where acceptor levels can also form, the combination of the nitrogen vacancy and the favored indium aggregation introduced even more levels at the top of the band gap, moreover examining the whole spin configuration we find a strong asymmetry in the occupation of the spin up and down states with a net moment of around 1 µB per supercell. Most importantly, the presence of a nitrogen vacancy changes significantly the top of the band gap: first, the band edges become very sharp, and second, the introduced states originating from local deformation are occupied. This leads to n type doping of the alloy and nicely agree with the use of Ti for generation of N vacancies in the technology of ohmic contacts on nitride materials. *Manuscript Click here to download Manuscript: CompMaterialSciencerevised2.docx Click here to view linked References

Stress relaxation in III-V nitrides: Investigation of metallic atoms interaction with the N-vacancy

“…Moreover, phase separation was reported during the annealing treatment of an InAlN at 72% In, where In-rich clusters size started to increase from about 6 Å at 600 • C as a function of time [28]. It may be pointed out that this radius of 6 Å corresponds to the size of the most stable In-rich cluster in InAlN in the above theoretical reports [52,53].…”

“…Indeed, In the growth of InAlN at 18% In, a degradation of the quality of the deposited layers has been observed [49][50][51]. Previous studies highlighted the possible role of native defects generated during the growth of InAlN layers at 18% In [52,53]. Moreover, phase separation was reported during the annealing treatment of an InAlN at 72% In, where In-rich clusters size started to increase from about 6Å at 600°C as a function of time [28].…”

Indium segregation mechanism and V-defect formation at the [0001] InAlN surface: an ab-initio investigation

“…Even with the high electronegativity of N (3.04), which is larger than that of Al (1.61) or In (1.78), there is a clear difference in the behavior of the In-N and Al-N bounds, aluminum nitride is the most stable of the three nitride, and indium nitride is the least stable [25]. As was recently shown, the bond is rather ionic in AlN, whereas it is partially covalent in InN [16]. On the defective InAlN surface, the In adatom (In a in fig.…”

“…The plane wave energy cutoff energy is 400 eV was determined as sufficient for the accurate calculation of the properties of AlN and InN in the wurtzite structure as shown in Table 1, along with experimental values, for the lattice parameters and elastic constants [16].…”

Electronic and magnetic properties of yttria-stabilized zirconia (6.7 mol% in Y2O3) doped with Er3+ ions from first-principle computations

“…:YSZ is an antiferromagnetic semiconductor with a gap of 5.20 eV which is about 0.4 meV per Er atoms more stable with respect to the ferromagnetic spin configuration. not take into account the weak peaks appearing around 4 eV of the CB which should be regarded as numerical artifacts due to the non-relaxed lattice constants [70,71].…”