Spontaneous Lateral Modulations in InAlAs Buffer Layers Grown by MBE on InP Substrates

Abstract

Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) have been used to analyze the spontaneous appearance of lateral composition modulations in InyAl1−yAs (yIn.≅ 50%) buffer layers of single quantum well structures grown by molecular beam epitaxy on exact and vicinal (100) InP substrates, at growth temperatures in the range of 530°C–580°C. The influence of the growth temperature, substrate misorientation and epilayer mismatch on the InAlAs lateral modulation is discussed. The development of a self-induced quantum-wire like morphology in the In0.53Ga0.47As single quantum wells grown over the modulated buffers is also commented on.

Initiation and evolution of phase separation in heteroepitaxial InAlAs films

“…1,2 Furthermore, in latticemismatched thin-film systems, the relative roles of morphological undulations and random compositional nonuniformities in the initiation of phase separation remain controversial. For example, in the InAlAs system, ͗110͘-oriented phase separation has been observed in bulk-like epilayers [3][4][5][6] and in short period superlattices 7 grown well above the miscibility gap temperature. In those cases, phase separation was attributed to spinodal decomposition, 4 morphological undulations, 6,7 and differences in Al and In sticking coefficients on stepped surfaces.…”

“…In those cases, phase separation was attributed to spinodal decomposition, 4 morphological undulations, 6,7 and differences in Al and In sticking coefficients on stepped surfaces. 5 In this letter, we report nanometer-scale investigations of the initiation and evolution of ͗110͘-oriented phase separation in the heteroepitaxial InAlAs thin film system. Our combined cross-sectional scanning tunneling microscopy ͑XSTM͒ and x-ray reciprocal space map ͑XRSM͒ studies suggest that phase separation is a misfit-driven kinetic process initiated by random compositional nonuniformities, which later develop into coupled compositional variations and morphological undulations.…”

Surface roughness in InGaAs channels of high electron mobility transistors depending on the growth temperature: Strain induced or due to alloy decomposition

“…The origin of such lateral domains could be related to strain-induced lateral ordering extensively reported for strained layers of semiconductors. 5,6 These previous studies have shown that the lateral composition modulation acts as a strain relieving mechanism that accommodates the mismatch between the epitaxial buffer layer and the substrate, depending on the growth temperature, substrate orientation, and layer-substrate mismatch. 6 In the present work, however, we have some substantial differences.…”

“…5,6 These previous studies have shown that the lateral composition modulation acts as a strain relieving mechanism that accommodates the mismatch between the epitaxial buffer layer and the substrate, depending on the growth temperature, substrate orientation, and layer-substrate mismatch. 6 In the present work, however, we have some substantial differences. First of all, we are dealing with a lattice matched channel system, and therefore, the lateral modulation should not have developed as a strain relieving mechanism.…”