Multiple-state resonant-tunneling bipolar transistor operating at room temperature and its application as a frequency multiplier

A resonant-tunneling bipolar transistor with two peaks in the direct as well as in the transfer characteristics is presented. The multiple peaks are obtained by sequentially quenching resonant tunneling through the ground states of a series of double-barrier quantum wells, placed in the emitter of a Ga0.47In0.53As/Al0.48In0.52As bipolar transistor, thus obtaining nearly equal peak currents and peak-to-valley ratios. The transistor exhibits current gain of about 70 at room temperature and 200 at 77 K. Peak-to-valley current ratios at room temperature and at 77 K are as high as 4:1 and 20:1, respectively. Frequency multiplication by factors of three and five has been demonstrated using the multiple-peak transfer characteristics of the transistor.