A. Raisanen

Reaction and growth of Yb/Hg1−xCdxTe(110) interfaces

Detailed synchrotron radiation photoemission studies of Yb/Hg1−xCdxTe junctions as a function of Yb coverage were performed at room temperature. Photoemission from physisorbed xenon after cooling the sample to 35 K was also used to examine the local overlayer work function and the development of interface morphology. For Yb coverages less than 6 A, the data provide evidence for the lateral growth of islands consisting of Yb‐Te reaction products involving divalent Yb, and an associated Hg depletion within an 18‐A‐thick near‐surface layer. Upon island coalescence at an Yb coverage of 6 A, the formation of a metallic Yb‐rich layer at the surface is observed. This layer traps Hg atoms diffusing across the interface through the formation of an Yb‐Hg alloy, and is responsible for the nonmonotonic behavior of the Hg interface concentration as a function of Yb coverage.

Engineering ZnSe-GaAs band offsets

Abstract High resolution synchrotron radiation photoemission studies of ZnSe-GaAs(110) heterojunctions prepared in situ on atomically clean substrates by low temperature molecular beam epitaxy were conducted using 80–130 eV photons. In addition, the effect of ultrathin Ge interface layers on the band offsets was examined by monitoring the energy separation of the Ga 2p and Zn 2p core levels at the interface with conventional X-ray photoemission spectroscopy. The results indicate that the natural (unmodified) valence band offset for ZnSe-GaAs(110) grown at low temperature is 1.10±0.05 eV, and that the fabrication of a Ge overlayer on GaAs prior to ZnSe deposition yields a decrease in the ZnSe-GaAs valence band offset. The offset decreases monotonically with Ge coverage in the 0.3–4 monolayers range and saturates for Ge thicknesses of 4–6 monolayers. The minimum measured valence band offset that we were able to achieve at the engineered interface is 0.93 ± 0.07 eV.

Yb diffusion barriers at Hg1−xCdxTe interfaces with Al, In, and Cr

Abstract We have performed synchrotron radiation photoemission studies of the formation of Hg 1−x Cd x Te/metal junctions in the presence of predeposited thin (3–15 A) Yb layers. Metals examined include Cr, In, and Al. Semi-empirical calculations of bulk binary thermodynamic parameters for each interface suggest that the rare-earth metal should act as an effective diffusion barrier. Correspondingly, we found that Yb interlayers reduce or eliminate metal-Te reaction, Te outdiffusion, and the Hg-depletion of the near-surface region in all cases examined.

Gd and Sm interfaces with Hg1−xCdxTe(110) and a general model of rare‐earth/Hg1−xCdxTe(110) interface formation

Room‐temperature synchrotron radiation photoemission studies of rare‐earth/Hg1−xCdxTe(110) junctions were performed as a function of metal coverage for the rare‐earth metals Sm, and Gd. These new results are compared to our previous results for Yb/Hg1−xCdxTe junctions. At low rare‐earth metal coverages, we observe in all cases a rare‐earth Te reaction which removes Hg and Cd from the interface region, and the three‐dimensional island growth of a rare‐earth telluride layer 4.0–4.5 monolayer thick. The most abrupt interface region is observed for Gd/Hg1−xCdxTe, in agreement with the more reactive character of this interface as compared to Yb/Hg1−xCdxTe and Sm/Hg1−xCdxTe. For higher rare‐earth metal coverages, we observe the formation of a metallic rare‐earth rich layer at the surface, which effectively traps Hg atoms diffusing across the interface through the formation of a rare‐earth–Hg alloy.

Enhanced Metallization Stability on Mercury-Cadmium-Telluride

Synchrotron radiation photoemission studies of ultra-thin Yb diffusion barriers at the interface between Mercury-Cadmium-Telluride semiconductors and Ag overlayers show that the interlayers act as effective diffusion barrier only after thicknesses of 10-15 A are reached. Studies of interlayer morphology by means of photoemission from physisorbed Xe indicate that effective diffusion barriers are consistent with a model in which a continous Yb-Te reacted layer is covered by an Yb-rich layer with high alloying enthalpy for Hg.