Metallurgical study of Ni/GaAs contacts. II. Interfacial reactions of Ni thin films on (111) and (001) GaAs

Abstract

The solid-state interactions at the Ni/(111) and (001) GaAs interfaces were investigated in the temperature range 25–600 °C by Rutherford backscattering spectrometry and channeling experiments, x-ray diffractometry, and four-point probe. The samples were prepared by depositing nickel films, 70 nm thick, onto clean (111) and (001) GaAs single-crystal substrates under 5×10−10 Torr vacuum. Then they were annealed for 1 h at increasing temperatures under a flow of forming gas (90% N2-10% H2). The sequence of phase formation was the following: first, a ternary phase at 200 °C, then a mixture of two ternary phases at 250 and 350 °C, and finally from 400 to 580 °C a mixture of a ternary phase and NiAs. This last structure was stable up to 600 °C on (111) GaAs, but at this temperature a further consumption of GaAs led to a mixture of (NiGa+NiAs) onto (001) GaAs. Small differences were observed versus the orientation of the GaAs samples but all the ternary and binary phases exhibited epitaxial arrangements with both the (111) and (001) GaAs substrates. The ternary-phase diagram for the bulk Ni-Ga-As system provides the basis for understanding the sequence of the above results and much of the information in the literature about Ni/GaAs interfacial reactions.

Comment on “Phase equilibria of the Ga–Ni–As ternary system” [J. Appl. Phys. 80, 543 (1996)]

“…Before comparing these conclusions to the experimental results, it is worth noting that Ingerly et al did not mention several of our papers on the Ni/GaAs interdiffusion [6][7][8] and which were based on the diagram of Guérin et al 3 In these papers, we reported both on the ordered phases which we found in the annealed Ni/GaAs contacts and also on the different steps of the Ni/GaAs interactions. In the two first papers, 6,7 the ordered ternary phases B, C, and E with hexagonal superlattices were unambiguously identified by transmission electron microscopy ͑TEM͒, while in the last one, 8 we proposed the detailed sequence of the Ni/GaAs interdiffusion, as shown in Fig.…”

“…In the two first papers, 6,7 the ordered ternary phases B, C, and E with hexagonal superlattices were unambiguously identified by transmission electron microscopy ͑TEM͒, while in the last one, 8 we proposed the detailed sequence of the Ni/GaAs interdiffusion, as shown in Fig. 3͑b͒.…”

“…Their results are compared to those of Guérin and Guivarc'h 3 and the authors claim that their re-examined Ga-Ni-As diagram allows one to better understand the mechanisms of interfacial reactions in Ni-based metallizations of GaAs. [4][5][6][7][8][9] The re-examination of the ternary phase diagram, by Ingerly et al especially in the Ni-rich region is based on the study of only 17 samples ͑denoted GNA 1 to 17͒ with various atomic compositions. In the work we presented in Ref.…”

The Physics of Semiconductors

“…3.24) is relevant for magnetic semiconductors, such as MnAs, and also occurs in the formation of Ni/GaAs Schottky contacts [60].…”

In situ controlled reactions and phase formation of thin films on GaAs

“…3,11,16,23 The ternary phase diagram also indicates that Ni 2 Ga 3 , and possibly NiAs 2 , are stable in contact with However, Ni x GaAs is not thermodynamically stable in contact with GaAs according to the ternary phase diagram.…”