Direct current and microwave characterization of integrated resonant tunneling diodes

Abstract

We present an integrated device fabrication sequence for GaAs/AlGaAs resonant tunneling diodes and the results of dc and microwave characterization of the integrated devices. The development of an integrated structure represents a first step toward monolithic or hybrid integration for applications such as oscillators in the 100 GHz–1 THz range. The use of a proton implant in addition to a mesa etch for device isolation allows low parasitic capacitance connections to bond pads, interconnects, or radiating elements. The dc and microwave measurement procedures and an equivalent circuit topology for the integrated device are described. Several features associated with the integrated geometry, including a decrease in peak current density with increasing device diameter, are observed in a study of the current-voltage characteristics of devices with various diameters. Contact resistances are determined from a physically based model and compared with experimental results. Microwave characterization techniques are used to obtain microwave equivalent circuit parameters for the integrated diodes. Device capacitance and conductance are presented as functions of device dimension and bias voltage. Parasitic circuit elements, including series resistance and a capacitance and resistance associated with the proton bombardment used to define the mesa, are also determined from the microwave analysis. The results obtained from microwave impedance measurements are compared with parameters obtained from dc characterization and numerical simulations of comparable device structures.