No abstract

No abstract

It has been theoretically ascertained that for defect-free InGaAs and InGaN compounds the uniform distribution of indium atoms is more energetically preferable than the clustering distribution. The presence of gallium and arsenic vacancy in InGaAs and nitrogen vacancy in InGaN facilitates indium atom clustering distribution. It has been shown that the increase in the indium content in InGaAs and InGaN compounds leads to the decrease of the formation energy of gallium, arsenic and nitrogen vacancies.

No abstract

PACS: 78.40.Fy; 78.45.+h; 78.55.Cr; 78.66.Fd Near-band-edge photoluminescence and reflection spectra have been investigated in GaN grown on Si and Al 2 O 3 substrates. It has been found that the doping of GaN both with Si and Mg reduces the value of compressive strain in GaN/Al 2 O 3 . In GaN/Si, no evidences of the crossover of A and B excitonic resonance positions with increasing tensile strain was observed. The calculations using the non-empirical SCF MO LCAO method showed that the Si Ga impurity may lead to an increase of the effective c/a lattice constant ratio, while Si N having greater formation energy produces a lattice relaxation which does not change the c/a ratio significantly. These results are in agreement with experimental observations of decreasing compressive strain in GaN : Si/Al 2 O 3 and increasing tensile strain up to the cracking in GaN : Si/Si.