Characterization of ZnSe/GaAs heterojunctions by SIMS and ellipsometry

✍ Scribed by M. Pirzer; B. Sailer; M.Ch. Lux-Steiner; E. Bucher; J.J. Dubowski; S.J. Rolfe

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 350 KB
• Volume: 185
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/0921-4526(93)90299-l

✦ Synopsis

P-ZnSe/GaAs heterojunctions, prepared by chemical vapour deposition (CVD) of ZnSe thin films on GaAs substrates at temperatures between 490 and 650°C were characterized chemically and optically. Depth profiling of Ga and Se concentrations by secondary ion mass spectroscopy yielded the CVD-growth temperature dependent diffusion coefficients D(T) = D,, exp(E,/kT) with E,, values of 3.4eV and 1.7 eV for Ga in ZnSe and Se in GaAs, respectively. Growth temperatures of about 560°C during a period of 3 h led to an interface about 1000 8, thick with gradually mixed chemical composition, still small compared to the width of the space charge layer. Optical characterization by spectral ellipsometry confirmed the nearly abrupt ZnSeiGaAs interface of junctions prepared at 575°C. As demonstrated by the comparison to simulated spectra, a mixed (ZnSe-GaAs) interface is not thicker than 200 A. Ellipsometric data at energies above the band gap of ZnSe indicated, however, the existence of a non-absorbing thin film surface layer due to the hygroscopic behaviour of ZnSe.