Properties of Ga-interstitial defects inAlxGa1−xNyP1−

Abstract

A detailed account of the experimental results from optically detected magnetic resonance ͑ODMR͒ studies of grown-in defects in ͑Al͒GaNP alloys, prepared by molecular beam epitaxy, is presented. The experimental procedure and an in-depth analysis by a spin Hamiltonian lead to the identification of two Ga i defects ͑Ga i -A and Ga i -B͒. New information on the electronic properties of these defects and the recombination processes leading to the observation of the ODMR signals will be provided. These defects are deep-level defects. In conditions when the defect is directly involved in radiative recombination of the near-infrared photoluminescence band, the energy level of the Ga i -B defect was estimated to be deeper than ϳ1.2 eV from either the conduction or valence band edge. In most cases, however, these defects act as nonradiative recombination centers, reducing the efficiency of light emission from the alloys. They can thus undermine the performance of potential photonic devices. High thermal stability is observed for these defects.

Defects in Dilute Nitrides

“…The observed anticorrelation between the intensity of the ODMR signals and the efficiency of the visible PL emissions strongly supports this conclusion (see Fig. 5) [22]. The revealed defects also seem to degrade thermal behavior of the PL emission leading to a severe quenching of the PL intensity at elevated temperatures [24].…”

“…Moreover, a dramatic suppression of the ODMR intensity was found after rapid thermal annealing (RTA) treatments of the Ga(In)NAs alloys, accompanied by a significant improvement in the radiative efficiency of the alloys - Fig. 3. Figure 4 shows typical ODMR spectra recorded at two microwave frequencies from Ga(Al)NP epilayers grown by MBE [21,22]. The strongest ODMR line in the middle of the spectra is related to a defect with a g-factor of 2.0079.…”

“…Therefore, we can conclude that the cores of both Ga i -A and Ga i -B defects involve a Ga atom, justifying the proposed defect notations. As a much higher strength of the hf interaction is predicted for isolated Ga interstitials in GaP [22], the observed defects are likely complexes involving a Ga i atom. The hf interaction is found to be insensitive to N compositions but strongly depends on Al compositions, indicating the likelihood of Ga i near the group-III sublattice.…”

Room-temperature defect-engineered spin filter based on a non-magnetic semiconductor

“…The difference between the Ga i defects in the RTA and as-grown samples lies at their neighbouring atoms and geometric locations. By using a one-electron linear combination of atomic orbital scheme 26 and the charge density of the 4s electron ( ) 2 4 0 s ψ =72.7x10 24 cm -3 for a free neutral Ga atom 25,27 , the localization of the electron wave functions at the Ga i 2+ defects is estimated to be 20% (as-grown) and 16% (RTA). The rather strong localization shows that they are deep-level defects, a prerequisite for efficient carrier recombination.…”

“…This is consistent with the observed strong hyperfine interaction, as the s-like electron wavefunction results in a strong Fermi contact term. The involved defects should then be in the Ga i 2+ charge state occupied by a single unpaired electron with an electronic state of A 1 symmetry, as the alternative Ga As antisite was predicted to possess a T 2 -symmetry state 24,25 . To quantitatively confirm this identification, we have carried out a detailed analysis of the ODMR results by a spin Hamiltonian…”