We make a two-dimensional analysis of field-plate AlGaN/GaN HEMTs with a Fe-doped semi-insulating buffer layer, and studied how the deep-acceptor density in the buffer layer NDA and the field-plate length LFP affect the breakdown voltage Vbr of AlGaN/GaN HEMTs. NDA is varied between 1017 cm-3 and 3×1017 cm-3, and the deep- acceptor’s energy level is set 0.5 eV below the bottom of conduction band. LFP is varied between 0 and 1 m. The calculated off-state breakdown characteristics show that the drain current usually increases steeply due to impact ionization of carriers, resulting in breakdown. But, in some cases, Vbr is determined by buffer leakage current. This current is larger for lower NDA, and hence Vbr becomes higher for higher NDA. It is also shown that Vbr takes a maximum value at LFP = 0.2-0.3 µm when the gate-to-drain distance is 1.5 µm, and that the average electric field for breakdown between gate and drain becomes 3.2 MV/cm when NDA is 3×1017 cm-3.
Journal: TechConnect Briefs
Volume: TechConnect Briefs 2019
Published: June 17, 2019
Pages: 458 - 461
Industry sector: Sensors, MEMS, Electronics
Topics: Informatics, Modeling & Simulation, Modeling & Simulation of Microsystems