Strain-relaxed epitaxial layers for high-speed electronic devices

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Abstract
A new approach of high‐speed electronic devices beyond the limit of pseudomorphic heterostructures is investigated. Metal‐semiconductor field‐effect transistors (MESFETs) are fabricated on InGaAs layers which have intentionally relaxed crystal lattice on GaAs substrate to take advantage of the small effective electron mass of bulk InGaAs materials. 0.25 μm gate MESFETs with an unstrained In0.15Ga0.85As layer and In0.25Ga0.75As layer show state‐of‐the‐art current gain cutoff frequencies of 120 and 126 GHz, respectively. These results imply a trade‐off between dislocation density and effective electron mass.