Temperature measurements by optical pyrometry during the epitaxial growth of semiconductors

The true and apparent temperature of samples during the deposition of III-V layers by molecular beam epitaxy changes as a result of the variation in spectral emissivity ϵ with layer thickness. Taking into account the infrared optical properties of these materials, we modelized the variations of the true sample temperature and the apparent temperature (as determined by pyrometric measurement) during the growth. We limited our study to deposits involving at least one absorbing material (at the pyrometer wavelength), for example GaSb, InAs or InSb. We showed that our simple model can agree reasonably with experiments in the 400−500 °C temperature range

Oscillations d'intensité RHEED liées aux mécanismes de croissance de GaSb par E.J.M.

Dans cet article, nous présentons une étude par la méthode des oscillations de l'intensité RHEED des mécanismes de croissance de GaSb par E.J.M. Nous avons précisé l'influence de différents paramètres (température du substrat, flux d'antimoine et de gallium, temps d'interruption de croissance) sur le régime oscillatoire et sur la stabilisation de l'intensité de la tâche spéculaire. L'analyse des courbes obtenues et leur évolution permet de corréler les résultats avec le processus de croissance et de préciser les mécanismes qui interviennent dans l'épitaxie par jets moléculaires du GaSb

Etude de l'effet de la température de dépôt ou de recuit sur la formation de l'interface Au/GaSb(100) par diffraction d'électrons lents et spectroscopies d'électrons Auger ou de pertes d'énergies

International audienceAuger electron spectroscopy (AES), energy electron loss spectroscopy (EELS) and low energy electron diffraction (LEED) are used to precise the interaction of gold with GaSb(100) surfaces grown on GaSb substrates by molecular beam epitaxy (MBE). After the growth, the GaSb layers, produced in the laboratory, were transferred by the mean of an ultra vacuum lock chamber, into an other ultra vacuum chamber devoted to the deposit of gold and to the physical studies. Measurements were first performed on the clean surfaces and then on surfaces covered by increasing amounts of gold (6 x 10(13) - 1.8 x 10(16) atoms cm(-2)) deposited on substrates brought at room temperature or at low temperature (220 K). The samples were then studied during the annealing up to 520 K. The results show that, at the beginning of the deposition, gold was adsorbed on the MBE GaSb(100) surface. When the gold coverage increases and becomes higher than 10(15) atomes cm(-2), Au diffuses into the bulk and forms alloys

Oscillations d'intensité RHEED liées aux mécanismes de croissance de GaSb par E.J.M.

We présent in this paper a study by RHEED oscillations intensities of the growth of GaSb by M.B.E. For this analysis we have studied the effects of different parameters (substrate temperature, antimony and gallium flux, the growth interruption time) on oscillation regimes and on the stabilisation of the specular reflexion intensity. The correlation of these results with growth process permitted us to clarify the MBE mechanism of GaSb.Dans cet article, nous présentons une étude par la méthode des oscillations de l'intensité RHEED des mécanismes de croissance de GaSb par E.J.M. Nous avons précisé l'influence de différents paramètres (température du substrat, flux d'antimoine et de gallium, temps d'interruption de croissance) sur le régime oscillatoire et sur la stabilisation de l'intensité de la tâche spéculaire. L'analyse des courbes obtenues et leur évolution permet de corréler les résultats avec le processus de croissance et de préciser les mécanismes qui interviennent dans l'épitaxie par jets moléculaires du GaSb

PROBLEMS RELEVANT TO THE USE OF OPTICAL PYROMETERS FOR SUBSTRATE-TEMPERATURE MEASUREMENTS AND CONTROLS IN MOLECULAR-BEAM EPITAXY

International audienc

Etude de l'effet de la température de dépôt ou de recuit sur la formation de l'interface Au/GaSb(100) par diffraction d'électrons lents et spectroscopies d'électrons Auger ou de pertes d'énergies

Auger electron spectroscopy (AES), energy electron loss spectroscopy (EELS) and low energy electron diffraction (LEED) are used to precise the interaction of gold with GaSb(100) surfaces grown on GaSb substrates by molecular beam epitaxy (MBE). After the growth, the GaSb layers, produced in the laboratory, were transferred by the mean of an ultra vacuum lock chamber, into an other ultra vacuum devoted to the deposit of gold and to the physical studies. Measurements were first performed on the clean surfaces and then on surfaces covered by increasing amounts of gold (6 $\times$ 10$^{13}$–1.8 $\times$ 10$^{16}$ atoms cm$^{-2}$) deposited on substrates brought at room temperature or at low temperature (220 K). The samples were then studied during the annealing up to 520 K. The results show, at the beginning of the deposition, gold was adsorbed on the MBE GaSb(100) surface. When the gold coverage increases and becomes higher than 10$^{15}$ atomes cm$^{-2}$, Au diffuses into the bulk and forms alloys.Nous étudions par spectroscopie d'électrons Auger (SEA), spectroscopie de pertes d'énergies d'électrons lents (SPEEL) et diffraction d'électrons lents (DEL), l'adsorption de l'or sur des surfaces (100) de couches de GaSb obtenues au laboratoire par épitaxie par jets moléculaires (EJM) sur des substrats de GaSb, puis transférées pour dépôt et étude dans l'enceinte à ultravvide de dépôt métallique par l'intermédiaire d'un sas sous ultravide. Les mesures sont effectuées avant et après dépôts d'or (6 $\times$ 10$^{13}$–1,8 $\times$ 10$^{16}$ atomes cm$^{-2}$) réalisés sur un substrat à la température ambiante ou refroidi à 220 K. Les échantillons sont ensuite étudiés pendant lerecuit jusqu'à 520 K. Les résultats obtenues montrent que l'or, dans un premier temps s'adsorbe sur la surface, puis, lorsque le dépôt augmente, diffuse dans le volume du matériau. cette diffusion, qui peut s'acompagner de la formation d'alliages, n'est cependant notable dans la gamme de température utilisée que pour des dépôts supérieurs à 10$^{15}$ atomes cm$^{-2}$

Structure, surface composition, and electronic properties of beta-In2S3 and beta-In2-xAlxS3

International audiencebeta -In2S3 and beta -In2-xAlxS3 thin films have been deposited on different substrates using the spray pyrolysis technique at 320 degreesC. X-ray diffraction, atomic force microscopy, and scanning electron microscopy were used to characterize the structure of the films; the surface compositions of the films were studied by Auger electrons spectroscopy and energy dispersive spectrometry (EDS), the work function and the photovoltage by the Kelvin method. Using these techniques, we have specified the effect of the nature of the substrate, of its surface morphology, of the introduction of small amounts of Al in the layer, on the properties of the films. The best crystallized of beta -In2S3 were obtained for deposits on pyrex. This was improved by the introduction of Al atoms. The work function differences (phi (material)-phi (probe)) for beta -In2S3 and beta -In2-xAlxS3 deposited on steel were equal to -150 meV and to -180 meV, respectively. Putting Al atoms in the film increases phi (m) (by about 30 meV) and induces the formation of a negative surface barrier. The concentration of In, S, and O elements increased when the samples were annealed under a vacuum, whereas the concentration of carbon decreased. The best composition was obtained for In2S3 deposited on SnO2 and annealed. The introduction of Al increases O and C concentrations and reduce In, Cl, and S concentrations. Analysis of the film compositions by EDS gives the following concentrations [In]=37%, [S]=52%, and [Cl]=11%. (C) 2001 American Institute of Physics

Preparation of GaSb(100) surfaces by ultraviolet irradiation

International audienceThe preparation of GaSb(100) surfaces by ultraviolet (UV) irradiation, prior to molecular beam epitaxy (MBE) growth, has been investigated. After optimization of the UV irradiation parameters (type of lamp, distance between the lamp and the sample, time exposure), GaSb surfaces present no detectable carbon contamination, a stoichiometry close to the MBE surface one, and a very good morphology. The oxide layers grown an the substrate surface have been analyzed by Auger electron spectroscopy and x-ray photoelectron spectroscopy. Large differences in the oxide composition, resulting from variations of the UV irradiation conditions, have been observed and analyzed. We discuss the experimental results and particularly the carbon desorption, in terms of oxide growth mechanisms and we propose a model of oxide growing in the optimal conditions. (C) 1997 American Vacuum Society

UV AND OZONE CLEANING OF GASB (100) SURFACES PRIOR TO MBE GROWTH

International audienceThe formation of sacrificial oxides by UV-ozone exposure on GaAs and InP is a well established procedure in the preparation of clean substrates for MBE growth. We describe a UV-ozone treatment used to prepare GaSb(100) substrates and report results obtained by Auger (Auger electron spectroscopy) which show that the quality of the so prepared substrates is excellent for MBE (molecular beam epitaxy)