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Chemical characterization of extra layers at the interfaces in MOCVD InGaP/GaAs junctions by electron beam methods.

Frigeri C, Shakhmin AA, Vinokurov DA, Zamoryanskaya MV - Nanoscale Res Lett (2011)

Bottom Line: A CL emission peak different from that of the QW was detected.By using HAADF, it is found that the GaAs QW does not exist any longer, being replaced by extra interlayer(s) that are different from GaAs and InGaP because of atomic rearrangements at the interface.The nature and composition of the interlayer(s) are determined by HAADF.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNR-IMEM Institute, Parco Area delle Scienze 37/A, 43010 Parma, Italy. frigeri@imem.cnr.it.

ABSTRACT
Electron beam methods, such as cathodoluminescence (CL) that is based on an electron-probe microanalyser, and (200) dark field and high angle annular dark field (HAADF) in a scanning transmission electron microscope, are used to study the deterioration of interfaces in InGaP/GaAs system with the GaAs QW on top of InGaP. A CL emission peak different from that of the QW was detected. By using HAADF, it is found that the GaAs QW does not exist any longer, being replaced by extra interlayer(s) that are different from GaAs and InGaP because of atomic rearrangements at the interface. The nature and composition of the interlayer(s) are determined by HAADF. Such changes of the nominal GaAs QW can account for the emission observed by CL.

No MeSH data available.


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CL spectrum A in the near-IR region of the investigated sample compared with that (B) of a sample exhibiting the expected GaAs QW emission. CL at 77 K with 5 keV beam energy.
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Figure 1: CL spectrum A in the near-IR region of the investigated sample compared with that (B) of a sample exhibiting the expected GaAs QW emission. CL at 77 K with 5 keV beam energy.

Mentions: Different electron beam energies were used to check the in-depth distribution of the layers. In the CL spectra at 77 K, bands corresponding to AlGaAs layer at 1.89 eV and InGaP layer at 1.94 eV were detected at the expected depth, indicating a composition of Al0.26Ga0.74As and In0.51Ga0.49P, respectively [12,13]. However, the emission from the GaAs QW was not detected; only a wide luminescence band at 1.48 eV, which could rather correspond to bulk GaAs, was observed as shown in the CL spectrum in the near-infrared (IR) region of Figure 1, where the CL emission A of the sample studied here is compared with the peak B of the GaAs QW (1.56 eV at 77 K) observed in a similar structure but containing the normal InGaP-on-GaAs interface, i.e. GaAs substrate/GaAs buffer/AlGaAs/GaAs/InGaP [12,13].


Chemical characterization of extra layers at the interfaces in MOCVD InGaP/GaAs junctions by electron beam methods.

Frigeri C, Shakhmin AA, Vinokurov DA, Zamoryanskaya MV - Nanoscale Res Lett (2011)

CL spectrum A in the near-IR region of the investigated sample compared with that (B) of a sample exhibiting the expected GaAs QW emission. CL at 77 K with 5 keV beam energy.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211250&req=5

Figure 1: CL spectrum A in the near-IR region of the investigated sample compared with that (B) of a sample exhibiting the expected GaAs QW emission. CL at 77 K with 5 keV beam energy.
Mentions: Different electron beam energies were used to check the in-depth distribution of the layers. In the CL spectra at 77 K, bands corresponding to AlGaAs layer at 1.89 eV and InGaP layer at 1.94 eV were detected at the expected depth, indicating a composition of Al0.26Ga0.74As and In0.51Ga0.49P, respectively [12,13]. However, the emission from the GaAs QW was not detected; only a wide luminescence band at 1.48 eV, which could rather correspond to bulk GaAs, was observed as shown in the CL spectrum in the near-infrared (IR) region of Figure 1, where the CL emission A of the sample studied here is compared with the peak B of the GaAs QW (1.56 eV at 77 K) observed in a similar structure but containing the normal InGaP-on-GaAs interface, i.e. GaAs substrate/GaAs buffer/AlGaAs/GaAs/InGaP [12,13].

Bottom Line: A CL emission peak different from that of the QW was detected.By using HAADF, it is found that the GaAs QW does not exist any longer, being replaced by extra interlayer(s) that are different from GaAs and InGaP because of atomic rearrangements at the interface.The nature and composition of the interlayer(s) are determined by HAADF.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNR-IMEM Institute, Parco Area delle Scienze 37/A, 43010 Parma, Italy. frigeri@imem.cnr.it.

ABSTRACT
Electron beam methods, such as cathodoluminescence (CL) that is based on an electron-probe microanalyser, and (200) dark field and high angle annular dark field (HAADF) in a scanning transmission electron microscope, are used to study the deterioration of interfaces in InGaP/GaAs system with the GaAs QW on top of InGaP. A CL emission peak different from that of the QW was detected. By using HAADF, it is found that the GaAs QW does not exist any longer, being replaced by extra interlayer(s) that are different from GaAs and InGaP because of atomic rearrangements at the interface. The nature and composition of the interlayer(s) are determined by HAADF. Such changes of the nominal GaAs QW can account for the emission observed by CL.

No MeSH data available.


Related in: MedlinePlus