Photoreflectance evidence of multiple band gaps in dilute GaInNAs layers lattice-matched to GaAs

Abstract

Dilute Ga1−xInxNyAs1−y∕GaAs quantum wells with high In-content, which are under compressive strain, have been shown previously to exhibit multiple band gaps, likely due to the presence of different nitrogen nearest-neighbor environments, i.e., N-Ga4−mInm(0⩽m⩽4) short-range-order clusters. Here, photoreflectance (PR) measurements on lattice-matched dilute GaInNAs-on-GaAs layers with low indium and nitrogen content are reported, which give evidence that these layers also exhibit several distinct band gaps. These distinct band gaps, which were found to coexist, are associated with different nitrogen bonding configurations, as revealed by Raman spectroscopy. Thus, the metastable nature of GaInNAs seems to be a persistent intrinsic property, irrespective of strain and indium content. The annealing-induced blueshift of GaInNAs band gap energy, which is usually observed in this system, has been associated with the change in the intensity of PR resonances related to different N-Ga4−mInm configurations.

Micro‐photoluminescence of GaInNAs layers grown on GaAs substrates of various crystallographic orientations

“…Such a scenario is often proposed for GaInNAs alloys [5] due to the large miscibility gap in this alloy [5,10]. However the origin of sharp PL lines is also associated with other localization centres in this material which are not related to alloy content fluctuations.…”

“…8. The change in µ-PL spectrum upon annealing is related to the reduction of point defects as well as the blueshift of GaInNAs energy gap which is associated with the change in the nitrogen-nearest neighbour environment, see for example the photoreflectance study of the energy gap for GaInNAs layers lattice matched to GaAs [10]. Because of the annealing induced blueshift of GaInNAs energy gap, the correlation between the nitrogen concentration and the energy gap of GaInNAs layers is a little bit different than this one which was observed in photoreflectance study of these layers before annealing, see Ref.…”

“…It is expected that deep donor-like and acceptor-like centres can be the source of exciton/carrier localization in this material at low temperatures [7,8]. Since the energy gap in GaInNAs significantly varies with the local alloy content as well the as nitrogen nearest-neighbour environment [10], it is expected that the localization energy for the same deep acceptor-like (donor-like) centres (the same from the structural viewpoint) can largely change from place to place due to various nearest-neighbour environments of these centres. As a result, almost continuous distribution of the sharp PL lines can be observed μ-PL spectra measured for various positions on the sample.…”

Electromodulation spectroscopy of In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum wells

“…In the case of PR spectra, a broad background-like signal is visible through the whole spectra whereas such a signal is not present in the CER spectra. The backgroundlike signal can be associated with below band gap oscillations which are often observed in the region of the sample transparency [24][25][26][27]. Such oscillations are usually very strong for GaAs-based structures grown on n-type substrates and they are weak or even invisible for GaAs-based structures grown on semi-insulating GaAs substrates.…”

Contactless electroreflectance spectroscopy of optical transitions in low dimensional semiconductor structures

“…an oscillation feature (OF) appear in PR spectra below the energy gap of GaAs if they are grown on n−type GaAs substrates [53,60,68,69]. Sometimes a weak OF is also observed for structures grown on semin− sulating GaAs substrates [61].…”