Monolithic integration of indium gallium arsenide/indium aluminum arsenide/indium phosphide electronic and optoelectronic devices and circuits.

Abstract

Recently, optoelectronic integrated circuits(OEICs) have generated interest for applications in both communication and radar systems. In the area of optoelectronic phased array radars, much work has focused on replacing the electrical distribution with optical distribution using fiber optics or optical waveguides. InP-based OEICs have demonstrated great potential due to 1.3-1.6 $\mu$m wavelength operation and high speed optoelectronic devices. The objective of the present research was to study the performance of discrete devices and circuits made with these materials and demonstrate their potential for the applications mentioned above. Pseudomorphic InGaAs/InAlAs modulation-doped field-effect transistors (MODFETs), grown by molecular beam epitaxy (MBE), with 0.1 $\mu$m T-shaped gate stripes have demonstrated extrapolated cutoff frequencies as high as 210 GHz which approach the state-of-art numbers reported by other laboratories. The first systematic study of the cryogenic microwave performance of these pseudomorphic MODFETs were done, and the gain and cutoff frequencies increased with lowering of temperature. The pseudomorphic InGaAs/InAlAs MODFETs were next used in a front-end photoreceiver circuit for high speed optical communication systems. Planar PIN-MODFET InP-based front-end photoreceivers realized using two-step MBE regrowth demonstrated large bandwidths of up to 6.5 GHz calculated from the temporal response of the circuit to a fast optical pulse. Also, the measured electrical 3-dB cutoff frequency was as high as 15.3 GHz with a 33 ohm input load impedance. Impurity induced layer disordering(IILD) was investigated on InGaAs/InAlAs superlattices to delineate optical waveguides to be used in future optoelectronic phased array systems. This is the first systematic study of this effect on InGaAs/InAlAs superlattices. Enhanced interdiffusion of Al and Ga in highly doped (Si and Zn) InGaAs/InAlAs superlattice structures have been observed. Due to a lower annealing temperature, IILD with Zn suppressed undesirable In modulations caused by the 'Darken effect'. The Zn IILD process was used to define an optical waveguide on an InGaAs/InAlAs MQW at 1.55 $\mu$m with a low loss of 2.3 dB/cm. The high performance pseudomorphic InGaAs/InAlAs MODFETs were applied towards realizing the high frequency monolithic microwave oscillators in an optoelectronic phased array system. A phased array system requires that the oscillators are frequency synchronized to a reference signal. To effectively enhance the locking range of the free running oscillators, optical tuning of the oscillators with a CW input light source can be used. The optical tuning characteristics of monolithically integrated InGaAs/InAlAs MODFET oscillators designed at X- and R-band demonstrated a maximum frequency shift of 8.7 and 11.7 MHz respectively with a 20 $\mu$W input light source.