Fig. 3

Room-temperature electrical characterization of variable thickness SrRuO₃ HETs. Common-base output characteristics (top) and voltage feedback (bottom) for SrRuO₃ thicknesses of a 10 u.c. and b 7 u.c., as J_E is increased from 0 to 5.36 mA cm⁻², in 1.34 mA cm⁻² steps; and c 1 u.c., as J_E is increased from 0 to 2.68 μA cm⁻², in 0.67 μA cm⁻² steps. The inset to a shows the region where clear transconductance can be seen for 10 u.c. SrRuO₃ thickness. The inset to b shows a schematic illustration of the increase of hot-electron transfer as the base becomes thinner. The constant voltage feedback curves in the common-base output characteristics demonstrate the complete electrostatic screening by the base metal. d Common-emitter output characteristics for 1 u.c. SrRuO₃ thickness, as J_B is increased from 0 to 2.68 μA cm⁻², in 0.67 μA cm⁻² steps. e Device statistics on common-base current gain α. For a specified SrRuO₃ thickness, each bar represents a single device and each color represents a distinct sample from a different fabrication run. f Common-base transfer characteristics for 1 u.c. SrRuO₃ thickness with V_CB ranging from 0.0 to 0.6 V, in 0.1 V steps. V_EB required for the onset of J_C is independent of V_CB, indicating pure HET operation.