Structural properties of InAs/InAs1–xSbx type-II superlattices grown by molecular beam epitaxy

Abstract

Strain-balanced InAs/InAs1−xSbx type-II superlattices (SLs) have been proposed for possible long-wavelength infrared applications. This paper reports a detailed structural characterization study of InAs/InAs1−xSbx SLs with varied Sb composition grown on GaSb (001) substrates by modulated and conventional molecular beam epitaxy (MBE). X-ray diffraction was used to determine the SL periods and the average composition of the InAs1−xSbx alloy layers. Cross-section transmission electron micrographs revealed the separate In(As)Sb/InAs(Sb) ordered-alloy layers within individual InAs1−xSbx layers for SLs grown by modulated MBE. For the SLs grown by conventional MBE, examination by high-resolution electron microscopy revealed that interfaces for InAs1−xSbx deposited on InAs were more abrupt, relative to InAs deposited on InAs1−xSbx: this feature was attributed to Sb surfactant segregation occurring during the SL growth. Overall, these results establish that strain-balanced SL structures with excellent crystallinity can be achieved with proper design (well thickness versus Sb composition) and suitably optimized growth conditions.

Investigation of MBE-grown InAs1−Bi alloys and Bi-mediated type-II superlattices by transmission electron microscopy

“…8(b) correspond to InAs layers while the peaks correspond to the InAsSb layers. The gradual intensity drop at the interface of InAs-on-InAsSb compared to the interface of InAsSb-onInAs indicated interfacial broadening, as observed previously for samples grown without any surfactant [13]. Thus, it appears that use of the Bi surfactant during growth did not significantly improve the asymmetrical interfacial abruptness.…”

“…Recent progress has been made in the design, growth and characterization of Ga-free InAs/InAs 1À x Sb x T2SL with very high structural quality, and the SL interface abruptness seems to play a significant role in affecting the emission properties [12][13][14]. Growth front coverage with surfactants of at most a few monolayer thickness has been used in MBE to help improve the surface/interface morphology and material properties.…”

Evaluation of antimony segregation in InAs/InAs1−xSbx type-II superlattices grown by molecular beam epitaxy

“…4,5 Ga-free InAs/ InAs 1Àx Sb x T2SLs grown with carefully chosen SL design for strain balance and proper control over growth conditions have very low densities of extended defects. 6,7 However, asymmetric SL peaks visible in high-resolution X-ray diffraction (HRXRD) patterns suggest the possibility of nonuniform InAs 1Àx Sb x layer thickness and/or Sb composition throughout the SL stack. Interface chemical diffuseness that is deduced based on evidence from scanning tunneling microscopy and transmission electron microscopy (TEM) may also be present.…”

Effects of AlSb interfaces on InAs/InAsSb type-II infrared superlattice material properties

“…18 It is visible under low excitation intensity when the lowest lying states are probed but not under high excitation intensity. Due to the As/Sb intermixing [19][20][21] in the InAs/InAsSb superlattice, this blue shift caused by composition non-uniformity is not surprising. The FWHM's are practically identical between samples over the entire temperature range, and the values range from 16 meV at low temperature to 44 meV at 200 K (Fig.…”