Gallium-arsenide surface passivation with aluminum-gallium - arsenide-nitride and zinc-selenide

David P Munich, Purdue University

Abstract

In this research we sought to passivate the GaAs surface with a dielectric which could potentially serve as the gate insulator for an MIS device technology. Passivation with AlN, AlGaAsN, and ZnSe were studied; heterojunctions of the three materials with GaAs were grown by MBE. Although none of the materials provided total surface passivation, important progress towards this goal was achieved. Quantum dielectric theory was extended to predict the likely properties of the AlGaAsN family of films. AlGaAsN crystal structure, band gap energies, and band edge discontinuities were investigated as functions of the Al and N mole fractions. The predicted properties of the AlGaAsN/GaAs heterojunctions indicate potential for AlGaAsN as a gate dielectric in a GaAs MIS structure. Experimentally, the formation of AlN/GaAs and AlGaAsN/GaAs heterojunctions was demonstrated. The predominance of the work described herein dealt with the heterojunction between ZnSe and GaAs. Operating MIS devices were fabricated for the first time on MBE-grown pseudomorphic ZnSe/GaAs heterojunction samples. C-V and I-V measurements revealed a somewhat nonideal device characterized by a high interface state density and current leakage between the GaAs and the metal gate. Standard C-V and I-V measurements did not totally characterize the ZnSe/GaAs heterojunctions. Specifically, the ZnSe insulator capacitance was unmeasurable and the existence of an inversion layer was uncertain. The ZnSe insulator capacitance was measured with a new quasi-static sweep technique which we proposed and implemented. A special overlapping gate CCD test structure was developed and employed to determine unequivocally whether an inversion layer existed at the ZnSe/GaAs interface. Measurements with the CCD failed to detect any minority carrier charge transfer, indicating the absence of an inversion layer at the ZnSe/GaAs interface.

Degree

Ph.D.

Advisors

Pierret, Purdue University.

Subject Area

Electrical engineering

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