Identification of heavy-hole and light-hole excitonic transitions is made by reflectivity and magnetocircular dichroism in strained metal-organic vapor-phase-epitaxy-grown ZnSe/GaAs epilayers with a thickness range between 0.10 and 0.78 mum at 4.5 K. The observed splitting of the exciton transitions due to the lattice mismatch is constant up to 200 K. It is explained by the very small variation (< 2%) of the lattice mismatch strain in this temperature range. Zeeman splitting of \+/- 3/2, +/- 1/2] and \+/- 1/2, -/+ 1/2] transitions are measured at 5.5 T and effective g values g3/2 = -0. 24 and g1/2 = 0. 5 7 are determined.

We have grown short-period ZnSe-ZnTe superlattices using low-pressure MOVPE. The influence of the growth parameters was investigated in detail. Combination of optical characterization with a tight-binding calculation gives a value of 200 meV for the strain-free valence band offset.

We present for the first time a detailed investigation of the growth of ZnTe layers deposited on GaAs substrates by low pressure metalorganic vapour-phase epitaxy using the new triethylamine dimethyl zinc adduct in combination with diisopropyl telluride as zinc and tellurium precursors respectively. The influence of the growth temperature (T(g)), the VI/II molar ratio, and the overall growth pressure (P) are studied. The successful growth of ZnTe is demonstrated at temperatures as low as 300-degrees-C. For growth temperatures ranging between 300 and 450-degrees-C, the growth rate is limited by the kinetics at the growing interface, and we measure an activation energy of 28 kcal/mol. At T(g) = 375-degrees-C, we found a linear variation of the growth rate with the overall growth pressure on the one hand, and with both zinc and telluride molar flows on the other hand. Low temperature reflectance and photoluminescence measurements were performed to characterize all the samples and are used to determine the optimal growth conditions: T(g) = 350-degrees-C, VI/II = 2, with P = 40 Torr. The stress experienced by the epilayers is investigated using the reflectance measurements. The relative intensity of the arsenic related bound exciton emission at 2.367 eV decreases as T(g) decreases. On the other hand, the I(b)1 unknown acceptor related bound exciton emission at 2.356 eV decreases linearly with the growth rate.

In this communication we show that the cancelation of excitonic effects by photo-injected carriers can be easily produced in ZnSe-ZnTe superlattices. This combination is interesting : it has a type II band alignment in real space. Strong confinements of electrons and holes by large bands offsets lead to important values of Rydberg energies ; thus, important energy-shifts of some 20 meV are measured when exciton screening is produced in such superlattices.

Non-intentionally doped ZnSe epilayers grown on (100) semi-insulating GaAs substrates by the MOVPE technique constitute heterostructures exhibiting "apparent" p-type conductivity, which we have investigated by Raman spectroscopy. The Raman spectrum of the substrate gives evidence of the presence of a p-type carrier gas in GaAs with p ranging from 10(18) to 10(20) cm-3, which appears as confined at the interface of ZnSe/GaAs. We have shown that the indium dots used for Hall-effect measurements diffuse through the epilayer up to the interfacial gas and concluded that this one is responsible for the large p-type conductivity of the samples. Moreover a quantitative analysis gives access to the interfacial gas thickness, typically 1000 angstrom.

Recently, III-V/II-VI single and double heterostructures have attracted much attention for device applications. The first demonstration of metal organic vapour phase epitaxy (MOVPE) of a GaAs/ZnSe/GaAs double heterostructure is reported. The influence of the ZnSe layer on the top GaAs layer is discussed from photoluminescence and reflectivity results.