Suppression of the kink effect in InGaAs/InAlAs HEMTs grown by MBE by optimizing the InAlAs buffer layer

The authors have examined the effects of InP substrate preparation and InAlAs growth temperature on the structural, electrical. and optical properties of In/sub 0.52/Al/sub 0.48/As layers grown on InP substrate. The substrate cleanliness affects the InAlAs growth mode while the growth temperature determines the kinetics of growth. It is concluded that the optimum InAlAs buffer layers have to be grown at T/sub G/=530 degrees C and the InP substrate has to be cleaned at T/sub t/=530 degrees C in order to obtain low defect density, smooth interfaces, and high resistivity with minimum carrier trapping or compensation centers. This optimization of the InAlAs buffer layer is of critical importance for the kink effect and, consequently, for the output conductance of the HEMTs (high electron mobility transistors) on InP. The optimized HEMT structures exhibited high transconductance, 530 mS/mm for 1- mu m gate length, low output conductance (19 mS/mm), and almost elimination of the kink effect on the I-V characteristics.<>