High-temperature stable MoAl2.7/n-GaAs Schottky diodes with enhanced barrier height

Abstract

High-temperature stable and smooth gate materials are required for self-aligned GaAs metal-semiconductor field effect transistor devices processing. Furthermore, the high Schottky barrier is beneficial to the GaAs digital logic circuits based on the enhancement mode field effect transistors. We report the high-temperature (up to 900 °C) stable MoAl2.7 Schottky contacts to n-GaAs with enhanced barrier heights from 0.67 to 0.98 V and low values of ideality factors after annealing. The surface of annealed contact is lustrous and smooth. The epitaxial AlxGa1−xAs layer, which induces the enhanced barrier height, at the interface of MoAl2.7/n-GaAs contact, has been clearly identified by the high-resolution cross-sectional transmission electron microscopy.

High-temperature stable Ir–Al/n-GaAs Schottky diodes: Effect of the barrier height controlling

“…4,5 It is possible to consider a generally accepted model of the barrier height enhancement based on the formation of a graded Al x Ga 1Ϫx As layer at M-Al/n-GaAs 4. 1͒ and Mo-Al/n-GaAs.…”

“…1,2,4,5,7 Since the formation of an interfacial Al x Ga 1Ϫx As layer should be a result of exchange reaction of Al and Ga by interdiffusion between Ir-Al multilayers and GaAs substrate, the barrier height enhancement should depend on annealing time and temperature as well as on a primary metallurgical microstructure of the interface. 1,2,4,5,7 Since the formation of an interfacial Al x Ga 1Ϫx As layer should be a result of exchange reaction of Al and Ga by interdiffusion between Ir-Al multilayers and GaAs substrate, the barrier height enhancement should depend on annealing time and temperature as well as on a primary metallurgical microstructure of the interface.…”

“…4,8 However, it is still difficult to determine the stoichiometry of the layer because of its grade composition and relatively small thickness. 4,8 However, it is still difficult to determine the stoichiometry of the layer because of its grade composition and relatively small thickness.…”

“…M-Al/n-GaAs contact systems, where M stands for Ni, 1 Co, 2 Pt, 3 or Mo, 4,5 appear to be potential candidates for gate contacts in these devices. Schottky gate contacts on GaAs with an enhanced barrier height and high thermal stability are required for devices based on heterostructures ͓heterostructure field-effect transistor ͑HFET͔͒ and self-aligned gate FET technology ͑SAG-FET͒.…”

“…The attention is now directed toward aluminum based metallic compounds. 1,2,4,7 The barrier height enhancement is attributed to the formation of a graded Al x Ga 1Ϫx As layer at the M-Al/n-GaAs interface as a consequence of an Al-Ga exchange reaction at elevated temperatures, and it can be explained by the larger energy band gap of Al x Ga 1Ϫx As than that of GaAs and the same pinning positions of the Fermi level at the metal/semiconductor interface. Some of these contact systems [2][3][4][5] are expected to replace contact systems based on refractory metal silicides and nitrides generally used in SAG-FET technology.…”