SURFACE-ROUGHNESS IN INGAAS CHANNELS OF HIGH-ELECTRON-MOBILITY TRANSISTORS DEPENDING ON THE GROWTH TEMPERATURE - STRAIN-INDUCED OR DUE TO ALLOY DECOMPOSITION

InAlAs/InGaAs/InP based high electron mobility transistor devices have been structurally and electrically characterized, using transmission electron microscopy and Raman spectroscopy and measuring Hall mobiliti es. The InGaAs lattice matched channels, with an In molar fraction of 53%, grown at temperatures lower than 530 degrees C exhibit alloy deco mposition driving an anisotropic InGaAs surface roughness oriented alo ng [1 (1) over bar 0]. Conversely, lattice mismatched channels with an In molar fraction of 75% do not present this lateral decomposition bu t a strain induced roughness, with higher strength as the channel grow th temperature increases beyond 490 degrees C. In both cases the prese nce of the roughness implies low and anisotropic Hall mobilities of th e two dimensional electron gas. (C) 1998 American Institute of Physics .