The epitaxial heterostructure GaN/AlGaN design effect on the device characteristics of power Ka-band HEMT

Research of a Ka-band HEMT was conducted. HEMT´s were manufactured with GaN/AlGaN heterostructures grown by MOCVD on sapphire substrates. A field-plate gate length and width was 0.15 μm and 400 μm correspondingly. A gate was placed between a drain and a source. Source contacts are connected to each other with double airbridges. It was shown that using of capsule layers i-GaN leads to ohmic contact resistivity reduction. It is shown that using of superlattice in a buffer layer leads to heteroepitaxial layers quality rise as well as leakage current reduction. This effect is achieved by buffer layer electron repulsion with negative charge localized at superlattice. Observed difference static IV caused by a capsule layer and superlattice presence leads to increasing f_T from 25 till 35 GHz and f_max from 68 till 80 GHz.