CdS was deposited onto clean cleaved InP(110) by molecular beam epitaxy (MBE) using a growth rate of 0.2 monolayers/min and a substrate temperature of 440 K (510 K). Raman spectra were taken in situ of the clean InP surface and after each evaporation step using an Ar+ ion laser as a light source. Due to this resonant excitation scattering signals originating from the CdS deposition are observed at coverages as low as 2 monolayers (ML). The number of phonon peaks observed and their selection rules reveal that the cubic modification is present. The spectra are dominated at all coverages by the longitudinal optical (LO) and 2LO phonon scattering intensities and the variation of the 2LO/LO intensity ratio with CdS deposition indicates changes in the electronic structure of the growing CdS. Another spectral feature in the Raman spectra is attributed to a chemically reacted layer at the interface most likely consisting of an In–S compound. The intensity of this feature is found to depend critically on the growth parameters, in particular the substrate temperature, but also on the operating time of the MBE cell. The amount of reaction at the interface also influences the critical CdS film thickness and the development of the 2LO/LO ratio. The results are discussed taking complementary photoluminescence, x-ray diffraction, and photoemission data into account.

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The heterojunction between silicon(111) and zinc sulfide was studied using Auger electron spectroscopy, photoelectron spectroscopy, and low-energy electron diffraction. Zinc sulfide layers were deposited onto cleaved Si(111) surfaces as well as Si(111)-(7×7) wafers by molecular beam epitaxy. The overlayers exhibited fair crystalline quality, and the characteristic valence-band spectrum of ZnS. The valence-band offset between the two semiconductors was determined from the core and valence-band spectra (ΔEv=−0.7 eV) and found to be much smaller than predicted. We attribute this disagreement, and the larger than usual scatter in our data, to the influence of interface dipoles in this polar interface, the density of which may partly be influenced by a varying amount of interface reaction.

A systematic knowledge of the influence of molecular-beam epitaxy growth parameters on the properties of AlGaAs/GaAs quantum wells grown under realistic growth conditions is important in order to obtain optimal performance of modern electronic and optoelectronic devices. Photoluminescence (PL) was used to investigate the influence of the Ga-controlled growth rate in the range below standard growth rates of 1 μm/h down to 0.1 μm/h, and of the As:Ga beam equivalent pressure ratio in the range of 10 to 60, on the growth kinetics, the interface quality, and the impurity incorporation, at a substrate temperature Ts =620 °C. As compared to in situ reflection high-energy electron diffraction (RHEED) measurements, where no sample rotation is possible, PL has the advantage that realistic growth conditions can be used. A careful line shape analysis, together with infrared and time-resolved PL measurements gives information on the interface roughness, the impurity incorporation, and the deep trap concentration. Non-negligible desorption of Ga during growth is found for the range of conditions under study. The desorption is found to increase upon a decrease of As:Ga ratio. The interface roughness as well as the impurity and trap incorporation are found to decrease with decreasing growth rate, an optimum interface quality being obtained below 0.5 μm/h. At this optimal growth rate, increasing the As4:Ga ratio leads to a decrease of shallow impurity concentration and thus to a narrower line width, but to a simultaneous increase of defect generation. Optimal growth conditions are found at a beam equivalent pressure ratio of 15. The observed desorption kinetics and interface properties can be explained in accordance with existing theoretical simulations. Finally, growth interruption was found to lead to optimal formation of flat growth islands when the overall growth rate is lowered.