Schottky barrier degradation of the W/GaAs system after high-temperature annealing

Abstract

W/GaAs diodes annealed at temperatures ranging from 100 to 900 °C were investigated with current voltage (I-V) and capacitance voltage (C-V) techniques, Rutherford backscattering spectrometry, scanning electron microscopy, and transmission electron microscopy. Improvements in the diode characteristics were observed after annealing at temperatures below 600 °C. Noticeable degradation in the rectifying behavior of the diodes occurred after annealing at temperatures >600 °C. Correlations between the electrical degradation and the interdiffusion of W and GaAs at the interface were found. Our results strongly suggest that the in-diffusion of W leads to the formation of a diffused, highly resistive region near the W/GaAs interface. The high resistance of this region is believed to be caused by the compensation of the substrate dopants by tungsten acceptors. Annealing the diodes at temperatures >850 °C resulted in reactions between W and GaAs. The W-GaAs reaction leads to islands of W2As3 at the W/GaAs interface, resulting in physical breakdown of the W/GaAs diode.

Effects of interface reactions on electrical characteristics of metal-GaAs contacts

“…The degradation of the Rh diode at >600°C is believed to be the effect of interdiffusion of the Rh and Ga and As atoms similar to the Pt diode [18]. Such interdiffusions are also observed for the W diode after annealing at temperatures >650°C and account for the degradation of the W diode at these temperatures [13]. The presented experimental data can be understood in terms of he recently proposed amphoteric defect model [10].…”

“…Table I behavior after annealing at 300°C and remains so up to 600°C. This can be attributed to the balling up of the native oxide at high temperatures resulting in an intimate contact between the W and the GaAs [13]. In addition, W, being the most electropositive of the metals studied, may react with the GaAs native oxide [14].…”

Metallurgy of M-GaAs contacts (M=W, Re, Si)

“…The only metastable phase observed by [1] was B-tungsten with an A15 crystal structure in as-deposited W films which transforms into the stable b.c.c, tungsten at 100 to 200 °C [10].…”

“…In order to understand the degradation mechanisms it is essential to know the thermodynamic and kinetic basis of the pertinent ternary Ga-As metal systems. For instance, data on thin-film W-GaAs contacts indicate the formation of tungsten arsenide at the interface after prolonged high-temperature annealing [1]. However, it has been shown in a preceding study of the ternary G~As W phase diagram [2] that no compound should form if the overall stoichiometry at the W-GaAs interface is undisturbed.…”

Correlation between solid-state reaction and electrical properties of the Rh/GaAs Schottky contact

“…In order to solve this problem, basic understanding of the metallurgy of various metal-GaAs interfaces is essential. Contact systerns such as Pt-GaAs [1][2][3], Pd-GaAs [3][4][5][6][7][8], Ni-GaAs [3,[9][10][11] and W-GaAs [1,[12][13][14][15] have been studied by many investigators. While most studies in this area have been concentrated on a few metal-GaAs systems, many other contact systems which may have great potential in technological applications have been neglected.…”