Molecular beam epitaxial growth of InAsSb strained layer superlattices. Can nature do it better?

Abstract

Molecular beam epitaxial growth of a normally homogeneous InAs0.5Sb0.5 alloy below 430 °C results in its coherent phase separation into platelets of two different alloy compositions with tetragonally distorted crystal lattices. This produces a ‘‘natural’’ strained layer superlattice (n-SLS) with clearly defined interfaces modulated in the [001] growth direction. A description of the n-SLS growth mode in InAsSb is outlined, and the optical response of a n-SLS structure, which extends to 12.5 μm−considerably further than that of a homogeneous InAs0.5Sb0.5 layer (8.9 μm)−is reported.

Band gap of InAs1−xSbxwith native lattice constant

“…13 These studies involved InAsSb grown on non-lattice matched GaAs substrates and low growth temperatures deliberately chosen to induce phase separation. This resulted in phase separation into platelets of two different alloy compositions, producing a natural strained layer superlattice, similar to those grown by Kurtz, et al 14 It is well known that such SLS structures produce smaller effective bandgaps than either of the constituent alloys.…”

Photoluminescence of InAs1−xSbx/AlSb single quantum wells: Transition from type-II to type-I band alignment

“…A band-gap reduction for MBE-grown InAs 1Ϫx Sb x random alloys has been reported, and is attributed to strain effects and natural phase separation. 11,12 The periodicity of our digital alloys is evident from the existence of satellite peaks in the single-crystal x-ray diffraction. 5 We have also carried out a tight-binding calculation for (InAs) n ͑InSb͒ 1 superlattices assuming a relaxed ͑i.e., free-standing͒ lattice constant and a valence band offset of 0.5 eV between unstrained InAs and InSb.…”

“…6 Owing to the small band gap, InAs 1Ϫx Sb x random alloys have been investigated for infrared detectors 9 and infrared lasers, 10 and have been grown by different methods including MBE. 11,12 In contrast, InAs 1Ϫx Sb x digital alloys were grown by MMBE in this work as described in Ref. 5, and characterized by high-resolution x-ray diffraction and infrared PL.…”

Impact of substrate temperature on the structural and optical properties of strain-balanced InAs/InAsSb type-II superlattices grown by molecular beam epitaxy

“…21 However, this composition is not ideal for long-wave infrared (LWIR) detectors due to the large lattice mismatch to the available III-V substrates (4.3% to GaSb, À1.8% to InSb). It was also reported that there is a large miscibility gap for InAs 1Àx Sb x alloys (from x ¼ 0.065 to 0.65 at 400 C), 22 and spontaneous phase separation was reported in InAs 0.50 Sb 0.50 MBE layers grown below 430 C. 23 Meanwhile, Sb surface segregation on InAs overlayers and As-for-Sb exchange in GaSb underlayers were reported at InAs/GaSb interfaces. 24 The same effects are expected to take place at InAs/InAs 1Àx Sb x interfaces, but Sb segregation can be suppressed more effectively at these interfaces because of the relatively low Sb/III ratio used during growth.…”