N. Q. Thinh

Mechanism for rapid thermal annealing improvements in undoped GaNxAs1−x/GaAs structures grown by molecular beam epitaxy

A systematic investigation of the effect of rapid thermal annealing (RTA) on optical properties of undoped GaNAs/GaAs structures is reported. Two effects are suggested to account for the observed dramatic improvement in the quality of the GaNxAs1−x/GaAs quantum structures after RTA: (i) improved composition uniformity of the GaNxAs1−x alloy, deduced from the photoluminescence (PL), PL excitation and time-resolved measurements; and (ii) significant reduction in the concentration of competing nonradiative defects, revealed by the optically detected magnetic resonance studies.

Formation of nonradiative defects in molecular beam epitaxial GaNxAs1−x studied by optically detected magnetic resonance

The formation of two nonradiative defects (i.e., an AsGa-related complex and an unknown deep-level defect with g=2.03) in GaNxAs1−x epilayers and GaAs/GaNxAs1−x multiple-quantum-well structures, grown by molecular beam epitaxy, is studied by the optically detected magnetic resonance technique. It is shown that contributions by these defects in competing carrier recombination strongly vary with the nitrogen composition. An increase in the growth temperature or postgrowth rapid thermal annealing significantly reduces the influence of the nonradiative defects studied, and is accompanied by a remarkable improvement in the optical properties of the structures.

Formation of Ga interstitials in (Al,In)yGa1−yNxP1−x alloys and their role in carrier recombination

Formation of complex defects involving a Ga interstitial (Gai) in (Al,In)yGa1-yNxP1-x alloys and their effects on optical quality are studied by photoluminescence (PL) and optically detected magnet ...

Ga-interstitial related defects in Ga(Al)NP

Two grown‐in Ga interstitial (Gai) defects in Ga(Al)NP are identified by optically detected magnetic resonance (ODMR), from the characteristic hyperfine (HF) structure associated with the nuclear spin I=3/2 of the Gai. Both defects are concluded to be Gai‐related complexes. Effects of Al and N compositions on the HF structure shed light on local surrounding of the Gai.

Nature and Formation of Non-Radiative Defects in GaNAs and InGaAsN

The optically detected magnetic resonance (ODMR) technique has been employed to examine the nature and formation mechanism of non-radiative defects in GaNAs and InGaAsN. In both alloys, two defects were observed and were shown to be deep-level, non-radiative recombination centers. One of the defects has been identified as a complex involving an AsGa antisite. These two defects gain more importance with increasing N composition up to 3%, presumably due to an increase in their concentration. With a further higher N composition, the defects start to lose importance in carrier recombination that is attributed to an increasingly important role of other new non-radiative channels introduced with a high N composition. On the other hand, effect of In composition up to 3% seems to be only marginal. Both defects were shown to be preferably introduced in the alloys during low-temperature growth by molecular beam epitaxy (MBE), but can be rather efficiently removed by post-growth rapid thermal annealing.

Optical and electronic properties of GaNAs/GaAs structures

We review our recent results from studies of electronic properties of GaNAs/GaAs structures with low nitrogen content, by photoluminescence (PL), PL excitation, time-resolved PL spectroscopies as well as optically detected magnetic resonance (ODMR) and cyclotron resonance (ODCR) studies. The issues to be addressed include key material-related properties and fundamental electronic parameters of the GaNAs alloy, relevant to device applications, such as identification of the dominant recombination processes in the alloy, compositional dependence of the electron effective mass and band alignment in the GaNAs/GaAs heterostructures.