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Soft X-ray photoelectron spectroscopy (SXPS) was performed on Si/Ge(111)-c(2 × 8) heterojunctions. The effect of an ordered ultrathin (one monolayer) ionic dipole layer of ZnSe placed at the interface was studied. The formation of the interface was monitored via the evolution of the valence band edges and the movements of core levels. It was found that the ZnSe intralayer dramatically modified the valence band offset of the Si/Ge (111) junction. The valence band offset was increased by 0.57 ± 0.1 eV due to the presence of the ZnSe intralayer. This intralayer-induced modification of the valence band offset is interpreted in terms of the charge transfer at the interface.

We have examined the physical and chemical reactions occurring during the formation of intimate In– and Au–InAlAs(100) at room temperature. In deposition results in a two-dimensional mode of growth, followed by clustering. Au deposition however, perturbs the interface with As diffusing into the Au overlayer. A Fermi shift is evident following the deposition of In and Au, but in both cases this is lower than barrier heights measured by transport techniques. Possible mechanisms for the observed adaptation of pinning position are discussed in the light of current models of Schottky barrier formation.

The control of semiconductor interfaces is essential to engineer new material properties for device applications. In this article we have considered the use of ultra-thin (1 monolayer) interfacial Si and Be dipoles layers to modify the band discontinuity present at the GaAs AlGaAs heterojunction. Soft X-ray photoelectron spectroscopy (SXPS) was performed at the Daresbury synchrotron radiation source (SRS) on samples previously grown by molecular beam epitaxy (MBE). Detailed deconvolution of the As 3d core level spectra enabled the valence band modification due to the presence of the interlayers to be extracted. The results of this study indicate the potential of this method to induce large valence band-offset modification (+0.4 eV for Si and −0.52 eV for Be) due to the presence of the dipole layers. The effect of any near interface doping by the Si and Be layers was considered by solving Poisson's equation for these structures. Finally, the technique is compared to other band engineering methods, namely δ-doping and multi quantum barriers (MQB), to assess the potential and viability for use in real devices.

The passivation properties of the Si GaAs(110) interface have been studied using scanning tunnelling microscopy/spectroscopy (STM/STS) and soft X-ray photoemission spectroscopy (SXPS). Silicon has been deposited at room temperature and STM images show the sub-monolayer growth of silicon islands on the GaAs substrate. The electrical properties of these islands together with the clean surface have been investigated using scanning tunnelling spectroscopy (STS). The spectroscopy clearly illustrates the difference in electrical properties between atomically flat regions of GaAs as compared to those containing defects or steps, i.e. where surface band bending occurs. We have investigated the use of sub-monolayer Si coverages to modify the electronic structure of the surface. Height variations of 3–4Aacross Si islands and 2Aacross steps on the GaAs surface have also been observed using the STM. STS spectra, collected simultaneously with the STM image, showed the Si to have semiconducting properties differing from that of crystalline Si and the GaAs substrate. Comparisons between the STM and STS results together with SXPS have provided a correlation between the structural, electrical and chemical nature of the Si/GaAs(110) interface.

Previous current–voltage studies of In contacts deposited on atomically clean (intimate) In53Ga47As(100) have indicated the potential to “select” barrier heights in this materials system by cryogenic processing. Soft x-ray photoemission spectroscopy was used to determine the electronic and chemical nature of these interfaces, as a function of formation temperature. Metallization at room temperature results in a predominantly three-dimensional mode of growth, accompanied by the outdiffusion of As. Low temperature metallization appears to reduce clustering and inhibit As outdiffusion. It is proposed that the distribution of surface states and the fermi level pinning position are altered by the changes that occur in the geometry and bonding of the interface at low temperature.

In this letter, the use of an ordered ultrathin ZnSe dipole layer to significantly modify the band discontinuity at the Si/Ge(111)-c(2×8) heterojunction is reported. Soft x-ray photoemission spectroscopy (SXPS) was utilized to monitor the evolution of the interface. The ZnSe intralayer increased the valence band offset by ∼0.57 eV, as compared to a negligible valence band offset for the Si/Ge(111) junction. This dramatic modification is interpreted in terms of the charge transfer at the interface.

The electrical, chemical and structural properties of the interfaces formed at room and low temperatures, between In and atomically clean In 53 Ga 47 As/InP(100) have been studied. Current-voltage measurements indicate that diodes formed at 80 K exhibit significantly higher Schottky barriers (φ b = 0.45 eV) than diodes formed at 294 K (φ b = 0.30 eV). The reactions occurring during the formation of In In 53 Ga 47 As/InP(100) interfaces at room and low temperatures have been investigated using Soft X-Ray photoemission spectroscopy. Our results show that metallisation at room temperature results in a predominantly three dimensional mode of growth, accompanied by the out-diffusion of As. Low temperature (125 K) metallisation appears to reduce clustering and inhibit As out-diffusion. Examination of the resulting interfaces by transmission electron microscopy confirms the more uniform nature of the metal layers formed at low temperature. These observations, in conjunction with the barrier heights measured by the I-V technique, are discussed in the context of currently supported models of Schottky barrier formation.