Temperature-graded InAlAs buffers applied on InGaAs/InAlAs/InP high electron mobility transistor heterostructures

In this work we studied the possibility of improving InGaAs/InAlAs-on-InP h igh electron mobility transistor (HEMT) devices by using temperature-graded InAlAs buffer layers with growing temperatures in the range of T-g = 250-5 60 degrees C. Our specimens were grown by molecular beam epitaxy and we ana lyzed them using plane view and cross-sectional transmission electron micro scopy, atomic force microscopy, scanning electron microscopy and Hall effec t measurements. We found that growth at the optimum temperature (T-g = 530 degrees C) of a thin InAlAs buffer sublayer between the InP substrate and t he thick InAlAs buffer layer (grown at low or high T-g) can dramatically im prove the crystalline quality of our HEMT devices. Therefore the growth tem perature of the buffer could be used as engineering parameter to tailor the electronic properties of InAlAs layers without interfering with the layers ' crystalline quality, already assured by the first optimized nanometers. ( C) 1999 American Vacuum Society. [S0734-211X(99)00506-5].