New double-barrier resonant-tunneling diodes have been fabricated in the pseudomorphic In053Ga47As/A1As material system that have peak current densities exceeding 1x105 A cnf2 and peak-to-valley current ratios of approximately 10 at room temperature. One of these diodes yielded oscillations up to 125 GHz, but did not oscillate at higher frequencies because of a large device capacitance. A device with a much lower capacitance is estimated to have a maximum oscillation frequency of 932 GHz and a voltage rise time of 1 .5 ps in switching from the peak bias point to the valley bias point. Other reported In053Ga47As/AlAs diodes are analyzed and yield theoretical maximum oscillation frequencies over 1 THz and rise times as low as 0.3 ps.