Gas-source molecular beam epitaxy growth of metamorphic InP/In0.5Al0.5As/In0.5Ga0.5As/InAsP high-electron-mobility structures on GaAs substrates

Advanced metamorphic high-electron-mobility heterostructures were grown by gas-source molecular beam epitaxy (gas-source MBE). These structures included an InGaAs/InAsP composite channel layers to improve breakdown voltage and a thin InP stopper layer under the n-InGaAs contact layer to provide long-term reliability and highly selective etching for mass production. Even though the graded buffer layer was thin (0.45 mum), misfit dislocations, observed by transmission-electron microscopy (TEM), were confined effectively to this thin buffer layer. High mobilities of over 9000 cm(2) V-1 s(-1) were obtained with the thin compositionally graded InAlAs buffer layer when the As composition of the InAsP sub-channel layer was less than 0.2.