Issues related to the usage of nitrogen as carrier gas for the MOVPE growth of GaSb/InAs heterostructures on InAs pseudosubstrates

TL;DR

This study explores the use of nitrogen as a carrier gas in MOVPE growth of GaSb/InAs heterostructures on InAs pseudosubstrates, highlighting growth conditions, electrical properties, and an unexpected decomposition process.

Contribution

It demonstrates the feasibility of GaSb growth with nitrogen carrier gas on InAs substrates and identifies optimal conditions including hydrogen addition and temperature effects.

Findings

GaSb growth with nitrogen is possible within narrow parameters.

Electrical tests show high electron mobility and specific 2D electron gas densities.

An unreported GaSb decomposition process occurs at low temperatures.

Abstract

GaSb/InAs/GaSb layer stacks have been grown on InAs metamorphic substrates (pseudosubstrates) by MOVPE, using nitrogen as major carrier gas. We demonstrate that GaSb growth by nitrogen MOVPE on InAs metamorphic substrates (and on InAs wafers) is possible in a very narrow range of growth parameters. As demonstrators, GaSb/InAs/GaSb structures were grown for electron mobility tests, obtaining (unintentional) 2D electron gas densities in the order of 9/5x10e12 cm(e-2) and mobilities up to 1.2/1.8x10e4 cm(e2)/Vs at room and liquid nitrogen temperature respectively. We show that it is beneficial to have some hydrogen in the carrier gas mixture for GaSb growth to achieve good crystal quality, morphology and electrical properties. Furthermore, an unexpected and previously unreported decomposition process of GaSb is observed at relatively low growth temperatures under the supply of the precursors for InAs epitaxial overgrowth. This nevertheless gets suppressed at even lower growth temperatures.