InGaAs/AlAs Resonant Tunneling Diodes for THz Applications: An Experimental Investigation

This paper presents an experimental study of InGaAs/AlAs resonant tunneling diodes designed to improve the diode characteristics using five different device structures. A promising high peak to valley current ratio of 5.2 was obtained for a very low current density device. As expected, the measured results show a significant increase in the current density with thinner barriers and quantum well widths. This is, however, at the expense of an increase in the peak voltages for high peak current density devices. A 36-mV/μm
²
voltage deviation was found for a diode with a peak current density of 10.8 mA/μm
²
that we attribute to self-heating of the diodes, and which were confirmed using pulsed dc voltage tests. To demonstrate how the self-oscillation at low frequency can be eliminated, a 25 Ω resistor was integrated in parallel with the diodes. The experimental findings suggest that the partially stabilizing resistor is limited by the absolute value of the negative differential resistance. The equivalent circuit of the diodes was validated using on-wafer S-parameter measurements up to 40 GHz. An estimated high frequency operation limit of 2.7 THz was deduced for RTD sample #327.