Photoluminescence studies of self-assembled InSb, GaSb, and AlSb quantum dot heterostructures

Abstract

Photoluminescence (PL) spectroscopy has been performed on a set of self-assembled InSb, GaSb, and AlSb quantum dot (QD) heterostructures grown on GaAs. Strong emission bands with peak energies near 1.15 eV and linewidths of ∼80 meV are observed at 1.6 K from 3 monolayer (ML) InSb and GaSb QDs capped with GaAs. The PL from a capped 4 ML AlSb QD sample is weaker with peak energy at 1.26 eV. The PL bands from these Sb-based QD samples shift to lower energy by 20–50 meV with decreasing excitation power density. This behavior suggests a type II band lineup. Support for this assignment, with electrons in the GaAs and holes in the (In,Ga,Al)Sb QDs, is found from the observed shift of GaSb QD emission to higher energies when the GaAs barrier layers are replaced by Al0.1Ga0.9As.

Deep level transient capacitance measurements of GaSb self-assembled quantum dots

“…A number of PL measurements have been published on GaSb dots made both in this laboratory 7 and others, 6,8 and they have associated a PL line at 1.14 eV with the recombination of an electron in the GaAs with a hole in the GaSb. This PL data is consistent with the DLTS reported here.…”

“…The data show a strong emission band near 1.14 eV at low excitation density. 6,7 This band has been found to shift to higher energy as the excitation power density is increased indicating a type II band structure. Further proof of the type II band structure, with the holes in the GaSb and the electrons in the GaAs, has been obtained by making PL measurements on GaSb dots grown on Al x Ga 1Ϫx As (xϭ0.1,0.2).…”

“…Photoluminescence ͑PL͒ experiments have demonstrated that GaSb QDs are significantly different from In x Ga 1Ϫx As/GaAs QDs are they have a type II band structure with a well in the GaSb valence band, which captures holes, and a barrier in the conduction band, which prevents the capture of electrons. [6][7][8] This band structure may be useful in electronic devices, particularly those requiring charge storage.…”

“…Further proof of the type II band structure, with the holes in the GaSb and the electrons in the GaAs, has been obtained by making PL measurements on GaSb dots grown on Al x Ga 1Ϫx As (xϭ0.1,0.2). 7 Details of the band structure for the GaSb self-assembled dots are difficult to predict as they are dependent upon the strain in the dots and the possible mixing of light and heavy 14 A variety of other experiments have been used to examine self-assembled GaSb quantum dots. The MBE growth parameters necessary for the formation of GaSb dots on GaAs have been determined by atomic force microscopy ͑AFM͒ measurements, [15][16][17] scanning tunneling microscopy, 18 and scanning electron microscopy 19 on uncovered GaSb dots.…”

Effects of interdiffusion on the band alignment of GeSi dots

“…13 In the type-II band alignment quantum structure, a band bending occurs at the interfaces due to the Hartree potential, as seen in the insets of Fig. 3͑b͒.…”