An enhancement/depletion process for III-V compound semiconductor heterostructure field-effect transistors and optoelectronic integrated circuits

Intense material and device research aimed toward high-speed digital circuits and optoelectronic integrated circuits (OEICs) has focused on III-V compound semiconductors such as GaAs-based and InP-based materials because of their superior electronic properties over those of silicon. Recent advances in the fields of Molecular Beam Epitaxy (MBE), Organometallic Vapor Phase Epitaxy (OMVPE), as well as device and circuit fabrication have made large-scale integration (LSI) using III-V compound semiconductor devices possible. This thesis describes an enhancement/depletion (E/D) process that utilizes modulation-doped field-effect transistors (MODFETs) and direct-coupled FET logic (DCFL) technology. The potential of this process for high-speed, high-density applications for LSI digital integrated circuits as well as optoelectronic circuits is demonstrated through the fabrication of the DCFL ring oscillators and the OEIC transimpedance receivers.; The success of this E/D process can be attributed to the selective wet etch process using citric acid:{dollar}rm Hsb2{dollar}O{dollar}sb2{dollar} solutions in conjunction with the introduction of the AlAs etch stop layers in the MODFET heterostructures. Extremely uniform device characteristics such as threshold voltage, extrinsic transconductance, and current-gain cutoff frequency have been achieved using citric acid:{dollar}rm Hsb2Osb2{dollar} solutions for gate recessing.; Discrete E/D MODFETs in both GaAs/InGaAs/AlGaAs and InP/InGaAs/InAlAs material systems exhibit good dc and high-frequency characteristics. Ring oscillators and OEIC receivers are fabricated successfully using this E/D process. The circuit yield is high. The ring oscillators exhibit a best gate delay of 13 ps, and the receivers show a bandwidth of greater than 3 GHz at a transimpedance gain of 50 dB. A maximum gain-bandwidth product of 2 THz{dollar}cdotOmega{dollar} is achieved for the receivers.