Increasing the current density of dielectric-base transistors with an MgO emitter-base barrier

We measured the current-voltage characteristics of YBa/sub 2/Cu/sub 3/O/sub 7-x//oxide/n-SrTiO/sub 3/ diodes using NdGaO/sub 3/, LaAlO/sub 3/, CeO/sub 2/, and MgO as the oxide. MgO films had the highest current density. We then fabricated dielectric-base transistors with a YBa/sub 2/Cu/sub 3/O/sub 7-x/(YBCO) emitter/collector on a SrTiO/sub 3/ dielectric base with an MgO barrier. The transistors had both voltage and current gains exceeding unity at 4.2 K. The emitter current density was about 4/spl times/10/sup 3/ A/cm/sup 2/ at a collector-emitter voltage of 10 V and base-emitter voltage 10 V; this is 2 to 3 orders of magnitude larger than that of transistors with NdGaO/sub 3/ emitter-base barrier. We obtained a transconductance of around 0.4 mS at a collector-emitter voltage of 10 V for a device with a 6-/spl mu/m-diameter emitter.>