Influence of the buffer layers on the morphology and the transport properties in InAs/(Al,Ga)Sb quantum wells grown by molecular beam epitaxy

Abstract

The growth of modulation-doped InAs/(Al,Ga)Sb quantum wells on GaAs substrates employing molecular beam epitaxy requires care in the nucleation and the use of buffer layers to achieve high quality material. Despite a 7% lattice mismatch between the substrate and the active layers, fully relaxed epitaxial growth can be accomplished, and quantum wells with electron sheet concentrations of 7×1012 cm−2 having low-temperature mobilities as high as 300 000 cm2/V s have been routinely fabricated recently in our laboratory. In the present work the combination of atomic force microscopy and van der Pauw measurements is used to investigate and explain the strong influence of the buffer layers on the morphology in the quantum well that is shown to be responsible for the great differences in the observed low-temperature mobilities.

High mobility metamorphic AlSb/InAs heterostructures grown on InP substrates

“…Kroemer's group has also shown that the roughness is different using an AlSb or a GaSb buffer grown on a GaAs substrate [3]. The roughness generated during the AlSb nucleation layer is smoothed by the growth of a GaSb layer although it is preserved by an AlSb growth.…”

“…The conventional technique of a Si plane in the barrier does not work because Si is amphoteric in III-V compounds and acts as a p-type dopant in antimonide-based materials [5]. An alternative solution consists in using Te as n-type dopant in the AlSb barrier [3]. Unfortunately, Te presents a high vapour pressure resulting in memory effects in the molecular beam epitaxy (MBE) chamber.…”

“…This mismatch is generally accommodated along a rather thick (typically 1-2 mm) buffer layer. Blank et al [3] studied the influence of this buffer (GaSb or AlSb) on the transport properties in AlSb/InAs quantum wells (QW). They have concluded that a smoother roughness is achieved using a GaSb buffer.…”

Comparison of short period InAs/GaSb superlattices on GaSb and GaAs substrates

“…The first key issue is the growth of low dislocation density GaAs-based SLs, since any roughness may lead to inferior lateral transport in the InAs/GaSb SLs [8] and in-homogeneity of the band gap. In our experiment, we used an AlSb interfacial misfit mode (IMF) quantum dot (QD) and an AlSb/GaSb SLs as the buffer layers on GaAs substrates.…”

Anisotropic transport properties in InAs/AlSb heterostructures

“…3 This results in a tensile strain in the InAs channel with respect to the AlSb metamorphic buffer leading to the formation of threading dislocations. 4 Anisotropic electron transport in HEMT devices based on strained layers of III-V alloys has been reported earlier. 5,6 However, no anisotropy behavior in InAs/ AlSb heterostructures has been reported so far.…”