Limits...
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.


Related in: MedlinePlus

(a) STEM-HAADF image of the whole structure. The nominal GaAs QW is the bright stripe between the InGaP and AlGaAs barriers. (b,c) HAADF intensity profile across (a) and only across the nominal GaAs QW at higher magnification, respectively. Intensity scan along the negative growth direction. In (c), 1 and 2 indicate the two sublayers replacing the nominal GaAs QW (see text).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211250&req=5

Figure 4: (a) STEM-HAADF image of the whole structure. The nominal GaAs QW is the bright stripe between the InGaP and AlGaAs barriers. (b,c) HAADF intensity profile across (a) and only across the nominal GaAs QW at higher magnification, respectively. Intensity scan along the negative growth direction. In (c), 1 and 2 indicate the two sublayers replacing the nominal GaAs QW (see text).

Mentions: To evaluate better the composition, the STEM-HAADF method was used. The STEM-HAADF image of the whole structure is given in Figure 4a. The intensity profile of Figure 4b shows that the contrast at the nominal GaAs layer is different from that of the GaAs substrate, confirming the DF results that the nominal QW is no longer made of GaAs. It also shows that the nominal GaAs well is made up of two sublayers, 1 and 2, with appreciable difference in HAADF contrast (Figure 4b,c); sublayer 1 (4 nm thick), which is closer to the GaAs-on-InGaP interface, with a contrast higher than the GaAs substrate, and sublayer 2 (6 nm thick), which is on the side of the AlGaAs barrier, with a lower contrast.


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)

(a) STEM-HAADF image of the whole structure. The nominal GaAs QW is the bright stripe between the InGaP and AlGaAs barriers. (b,c) HAADF intensity profile across (a) and only across the nominal GaAs QW at higher magnification, respectively. Intensity scan along the negative growth direction. In (c), 1 and 2 indicate the two sublayers replacing the nominal GaAs QW (see text).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: (a) STEM-HAADF image of the whole structure. The nominal GaAs QW is the bright stripe between the InGaP and AlGaAs barriers. (b,c) HAADF intensity profile across (a) and only across the nominal GaAs QW at higher magnification, respectively. Intensity scan along the negative growth direction. In (c), 1 and 2 indicate the two sublayers replacing the nominal GaAs QW (see text).
Mentions: To evaluate better the composition, the STEM-HAADF method was used. The STEM-HAADF image of the whole structure is given in Figure 4a. The intensity profile of Figure 4b shows that the contrast at the nominal GaAs layer is different from that of the GaAs substrate, confirming the DF results that the nominal QW is no longer made of GaAs. It also shows that the nominal GaAs well is made up of two sublayers, 1 and 2, with appreciable difference in HAADF contrast (Figure 4b,c); sublayer 1 (4 nm thick), which is closer to the GaAs-on-InGaP interface, with a contrast higher than the GaAs substrate, and sublayer 2 (6 nm thick), which is on the side of the AlGaAs barrier, with a lower contrast.

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