DIRECT-CURRENT AND MICROWAVE CHARACTERIZATION OF INTEGRATED RESONANT-TUNNELING DIODES

We present an integrated device fabrication sequence for GaAs/AlGaAs r esonant tunneling diodes and the results of de and microwave character ization of the integrated devices. The development of an integrated st ructure represents a first step toward monolithic or hybrid integratio n 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 isolati on allows low parasitic capacitance connections to bond pads, intercon nects, or radiating elements. The dc and microwave measurement procedu res and an equivalent circuit topology for the integrated device are d escribed. Several features associated with the integrated geometry, in cluding a decrease in peak current density with increasing device diam eter, are observed in a study of the current-voltage characteristics o f devices with various diameters. Contact resistances are determined f rom a physically based model and compared with experimental results. M icrowave characterization techniques are used to obtain microwave equi valent circuit parameters for the integrated diodes. Device capacitanc e and conductance are presented as functions of device dimension and b ias voltage. Parasitic circuit elements, including series resistance a nd a capacitance and resistance associated with the proton bombardment used to define the mesa, are also determined from the microwave analy sis. The results obtained from microwave impedance measurements are co mpared with parameters obtained from de characterization and numerical simulations of comparable device structures. (C) 1995 American Instit ute of Physics.