Epitaxial growth of ZnSiN2 single-crystalline films on sapphire substrates

International audienceA new family of wide band gap nitride semiconductors expressed as II-IV-N-2 have recently attracted attention due to their expected properties such as optical non-linearity. In addition, among these compounds, ZnGeN2 and ZnSiN2 have lattice parameters close to GaN and SiC respectively. Up to now, there is very little work reported on this class of materials and no systematic thin film growth study has been reported to date. In this paper we present the first study on the growth of ZnSiN2 on c-sapphire and (100) silicon substrates using low pressure MOVPE technique. Triethylamine:dimethylzinc adduct, silane diluted in H-2 and ammonia were used as source materials. Single crystalline epitaxial ZnSiN2 layers were obtained on nitridated c-sapphire substrates in the temperature range 873-973 K by using an adapted II/IV molar ratio ranging from 1.2 to 12. Assuming an orthorhombic unit cell, the lattice parameters calculated from the X-ray diffraction data are a = 0.534 nm, b = 0.617 nm and c = 0.504 nm

ZnCdSe-ZnSe heterostructures grown by MOVPE

International audienceWe have grown graded index separate confinement heterostructures (GRIN-SCH) for microgun blue-green laser by low pressure MOVPE. A first study was carried out using selenium hydride, dimethyl cadmium and two dimethylzinc adducts as Se, Cd and Zn precursors respectively. This combination leads to intense prereactions and poor layer morphology. To limit this problem we have then used the tetrahydrothiophene:dimethylcadmium adduct. We have first investigated the quality of thick ZnCdSe layers grown using the two sets of precursors. Then, GRIN-SCH structures grown using the two cadmium metalorganics were studied using photoluminescence and optical pumping experiments. (C) 1997 Elsevier Science S.A

Optical properties of ZnSe-ZnTe type II superlattices

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

Optical gain in ZnS epilayers

International audienceThe variable stripe length method is used to study optical gain in MOVPE-grown ZnS/GaAs epitaxial layers. Optical gain and spontaneous emission spectra are extracted from experimental results. A net optical gain of about 30 cm−1 under excitation by a XeCl laser having a power density of 100 kW cm−2 is observed at very low temperatures (T < 20 K) and it is rapidly quenched for higher temperatures. Gain is interpreted to be due to stimulated emission from the bound exciton state and from the biexciton ground state towards free exciton levels. The spectral shape of the gain spectrum is well fitted by the sum of these two contributions. Smaller gain at lower photon energies is obtained due to exciton-excition collisions

Light amplification due to free and localized exciton states in ZnCdSe GRINSCH structures

International audienceIn this paper we present measurements of light amplification in optically pumped ZnCdSe GRINSCH (graded refraction index separate confinement heterostructures), In several differently designed samples we observe the presence of two gain mechanisms, which involve localized excitons and exciton-exciton inelastic scattering processes, respectively. The influence of the GRINSCH sample structure on gain is discussed in terms of their improved light-guiding properties