Design, fabrication and characterization of GaN based high electron mobility transistors (HEMT)

In this study, novel epitaxial structures for GaN based high electron mobility transistors (HEMT) have been designed and grown by using MOCVD technique. Electrical and structural characterizations of the grown samples have been performed. AlGaN/AlN/GaN HEMTs with InGaN back barriers, AlInN/AlN/GaN HEMTs with AlGaN buffers and AlInN/AlGaN double barrier HEMT structures were grown and material properties were analyzed. AFM and high resolution XRD techniques were used for structural analysis, temperature (30-300K) and magnetic field (0-1,4 Tesla) dependent Hall Effect system was used for electrical analysis. Dominant scattering mechanisms were determined for the samples. Increase in electron confinement and mobility has been observed in the samples with InGaN back barriers. Transistor devices were fabricated on the samples with AlInN barriers and characterized. Effects of epitaxial structure design on the performance of HEMT devices were examined. Lower leakage currents and higher breakdown voltages were obtained in AlInN HEMT structures with AlGaN buffer layers when compared to the structures with standard GaN buffer layers.Key Words : AlInN, AlGaN, GaN, HEMT, Hall effect, Scattering