Growth-temperature optimization for low-carrier-density In0.75Ga0.25As-based high electron mobility transistors on InP

Two-dimensional electron gases (2DEGs) were formed in undoped In0.75Al0.25As/In0.75Ga0.25As/In0.75Al0.25As quantum wells. The optimal growth temperature for this structure is 410 degrees C, with peak 2DEG electron mobility and density values of mu=221 000 cm(2)/V s and n=1.36x10(11) cm(-2) at 1.5 K. This electron mobility is equal to the highest previously published for these undoped structures but with a factor of 2 reduction in n. This has been achieved through the use of a significantly thinner InAlAs graded buffer, which supports the theory that this is the source of the 2DEG electrons. For n>1.6x10(11) cm(-2), mu is shown to be 10% higher for transport parallel to the [011] crystal axis. This is a direct result of anisotropic surface morphology. (C) 2007 American Institute of Physics.