High-Temperature Microwave Performance of Submicron AlGaN/GaN HEMTs on SiC

Analysis of AlGaN/GaN high electron mobility transistors with nonalloyed Ohmic contacts achieved by selective area growth using plasma assisted molecular beam epitaxy

“…Moreover, the drain current degradation at V GS = 10 V for HEMT-B is only 3.4%, much smaller than that of HEMT-C (12.3%). It has been reported that the current degradation is partially caused by the crystallographic-defects, which act as the electron trapping sites [8]. When these defects are charged by the applied drain bias, the 2DEG sheet carriers are depleted, resulting in a decrease in the drain current.…”

“…However, the high temperature annealing process takes advantage of the reaction between the metals and GaN to form metallic TiN, while the residual nitrogen vacancies acting as donors that increases the doping concentration of n-GaN under the metal contacts. As a consequence, the accumulation of surface defects created in the process may cause adverse effects such as reliability problem under high temperature operations and current degradation under high voltage [8,9]. In addition, the high temperature process causes severe lateral diffusion of the contact metals, hindering further downscaling of GaN-based high-frequency transistors.…”

Influence of temperature and drain current on source and drain resistances in AlGaN/GaN HEMTs

“…The use of variable parasitic resistances allows more accurate values of the intrinsic parameters, since the extraction of the intrinsic circuit depends on the extrinsic parameters such as R S , R D , R G , and some parasitic capacitances and inductances. All the details about the extrinsic circuit and its high temperature dependence can be found in [6]. Although R G also changes with T amb , its relative variations are lower than those of R S or R D [6]; in addition, it does not seem to be affected by high I D .…”

“…Several works have focused on the extraction of the equivalent circuit parameters (ECP) not only at room temperature (RT) [3,4], but also at low [5] and high T amb [6,7]. Among all the ECP, the parasitic source and drain resistances (R S and R D ) play a relevant role: as they are smaller, the real HEMT behavior becomes closer to the ideal case, which means better DC (I D , g m ) and RF (f T , f max ) performance.…”

“…Different works deal with the parasitic resistances [3][4][5][6][7][8][9][10][11], either experimentally or by modeling, though only a few study their evolution with temperature [8,9] or its dependence on drain current (I D ) at RT [10,11]. Both T amb and I D dependencies of parasitic resistances are interesting by themselves, but a global study including both effects is quite useful for a better calculation of the equivalent circuit.…”