Investigation of Surface Defects in AlInSb Metamorphic Buffer (MB) Grown on GaSb

Journal of ELECTRONIC MATERIALS, Vol. 45, No. 12, 2016

DOI: 10.1007/s11664-016-5032-1

2016 The Minerals, Metals & Materials Society

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SADHVIKAS ADDAMANE,1,2 DARRYL SHIMA,1 AMY LILI SOUDACHANH,1 CHRISTOPHER HAINS,1 RALPH DAWSON,1 and GANESH BALAKRISHNAN1

1.Center for High Technology Materials, 1313 Goddard St. SE, Albuquerque, NM 87116, USA.2.e-mail: [email protected]

We have conducted an investigation of the different surface defects observed on InAlSb metamorphic buffers grown on GaSb. There are two different defect modes found in this system: crystallographic surface features and surface cross-hatching. We have characterized both defect modes using optical microscopy, scanning electron microscopy, and plan-view and cross-sectional transmission electron microscopy. It is found that particulates from polishing slurry or incomplete oxide desorption on the substrate before the growth are the root of the crystallographic defects. Surface crosshatching is shown to be caused by the coalescence of strained islands formed at the onset of buffer layer growth. Despite the presence of these defects, we have shown that substantial areas of the surface are defect-free and can be effectively used for realizing devices on this platform. Threading dislocation and crystallographic defect densities are found to be 1 9 107/cm2 and 5 9 104/cm2, respectively.

Key words: Metamorphic buffer, InAlSb, crystallographic defects, surface cross-hatching

INTRODUCTION

Mid-wavelength infrared (MWIR) lasers are of interest for a variety of applications including gas detection, environmental monitoring, and infrared countermeasures. Traditionally, these lasers have been based on Type-I InGaAsSb/AlInGaAsSb quantum well (QW) active regions grown lattice-matched to GaSb substrates, and recent developments in this material system have yielded devices with low threshold power and high operating temperatures.15 However, the growth of these structures usually requires composition control using two group V elements, which is fundamentally difcult to control during molecular beam epitaxy (MBE) growth. In addition, the growth of some compositions of InxGa1 xAsySb1 y is not straightforward

due to the existence of a large miscibility gap, which may result in random regions with non-uniform alloy composition.6 By removing the lattice-

matching condition and using a metamorphic buffer with a lattice constant larger than GaSb, devices with only one group V element based on the InGaSb/ InGaAlSb system can be realized. In addition,...