through the silicon carbide however the dissipated heat ends up at a free air top surface 34 of the silicon carbide substrate which carries no heat sink thus the removal of heat from the rf amplifier stymied at the free air surface with the die heating up in the absence of a heat sink referring to fig3 the outline of a typical high power rf amplifier includes a gate structure 36 with associated fingers surrounding a drain 40 with grounded source electrodes 42 to either side of the gate drain structure if an rf signal as indicated by 44 is applied to a vertically transitioning metalized via 50 then a microstrip or patterned conductor 51 is utilized to convey the energy from the center pin of a coax transmission line in this case to gate structure 36 with the vertically transitioning wall metalized via 50 running from the bottom of the silicon carbide substrate 58 up through an etched hole in the gallium nitride layer 56 where it contacts conductor 51 in order to couple rf signals as illustrated at 53 to gate 36 it will be appreciated that sources 42 may be grounded by a metalized via shown in dotted outline at 44 to the.