Metamorphic Devices

Authored by: John E. Ayers , Tedi Kujofsa , Paul Rago , Johanna E. Raphael

Heteroepitaxy of Semiconductors

Print publication date:  October  2016
Online publication date:  October  2016

Print ISBN: 9781482254358
eBook ISBN: 9781315372440
Adobe ISBN:


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The metamorphic approach is often preferred for device fabrication because it allows considerable freedom in choosing layer compositions and thicknesses when compared with pseudomorphic growth. An important example of this is the InxGa1−xAs/InyAl1−yAs-based high-electron-mobility transistor (HEMT) grown on a GaAs substrate. The indium content in the quantum well must be limited to less than 20% if pseudomorphic growth is to be achieved on GaAs substrates, while use of InP substrates allows lattice matching with ∼50% indium content. On the other hand, InxGa1−xAs/InyAl1−yAs HEMTs with virtually any indium composition may be fabricated on GaAs substrates using metamorphic buffer layers, avoiding the need for InP substrates and extending the performance of the resulting transistors. The same is true for HEMTs based on other material systems grown metamorphically on GaAs substrates. It is still desirable to grow the quantum wells coherently strained to the confining layer material, but this is far less restrictive when using lattice-relaxed metamorphic buffer layers that can adopt any lattice constant within a wide range spanning from GaP(0.5451 nm) to GaSb(0.6096 nm).

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