Peculiarities of Ga2te3 Thermal Oxidation O.A
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ARTICLE IN PRESS Materials Science in Semiconductor Processing 10 (2007) 124–127 Peculiarities of Ga2Te3 thermal oxidation O.A. BalitskiiÃ, V.P. Savchyn Department of Electronics, Lviv Ivan Franko National University, Dragomanov str., 50, 79005 Lviv, Ukraine Available online 2 April 2007 Abstract The processes of Ga2Te3 were studied using X-ray photoelectron spectroscopy, X-ray diffraction and cathodolumines- cence methods. It was found, that Ga2Te3 oxidised stepwise with amorphous gallium oxide and tellurium dioxide formed at the beginning followed by crystallisation of Ga2O3 and tellurium trioxide volatility losses. The temperature intervals of intermediate phases existence in own oxide film were established. The similarity in oxidation mechanisms in bulk and on the surface is discussed. r 2007 Elsevier Ltd. All rights reserved. PACS: 81.65.M Keywords: Ga2Te3; Own oxide; Thermal oxidation 1. Introduction sesquitelluride could, in one hand, be used as a method of heterostructures fabrication, as it was Gallium sesquichalcogenides ðGa2Te3; Ga2Se3; done for the other III–VI compounds [6].On Ga2S3) belong to the large class of materials with the other hand, the surface properties of Ga2Te3 cubic sphalerite low temperature a-modification. are key factors controlling the properties of the Among the other III–VI compounds Ga2Te3 structures containing this compound. So the aim seemed to be the less studied. Few works are of this work is the development of gallium devoted to the electric and ferroelectric properties of sesquitelluride own oxide composition and estab- Ga2Te3 [1,2]. Meanwhile Ga2Te3 attracts the atten- lishing intermediate phases sequence, formed during tion of the researcher due to its formation on the oxidation. interface boundaries of epitaxial ZnTe/GaSb struc- tures [3–5]. Contrary to the GaAs–ZnSe interfaces 2. Experimental where appearance of Ga2Se3 positively affects the properties of the structure due to zinc selenide For the investigation we used Ga Te samples, structure perfecting, Ga2Te3 drastically decreases 2 3 the quality and electrical properties of correspond- obtained from the initial elements with purity not ing structures. The own oxide formation of gallium less than 99.999%. By X-ray diffraction (XRD) it was proved that samples were crystallized in a low ÃCorresponding author. temperature cubic a-modification with lattice para- E-mail address: [email protected] meter a ¼ 0:5898 nm being in good agreement with (O.A. Balitskii). individual crystallographic data [7]. The oxidation 1369-8001/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.mssp.2007.02.001 ARTICLE IN PRESS O.A. Balitskii, V.P. Savchyn / Materials Science in Semiconductor Processing 10 (2007) 124–127 125 was conducted in 4002900 C temperature interval practically is not affected by the oxidation. The in the air. appearance of high energy shoulder at 23.6 eV (Fig. 1b) For the phases detection in own oxide film X-ray is a result of oxygen 2s emission. The same situation photoelectron spectroscopy (XPS) of core levels, was observed both for core 2p and Auger LMM XRD and cathodoluminescent (CL) properties were levels of gallium (not shown). This is caused by the examined. XPS patterns were recorded using a PHI coincident of the chemical shifts of gallium levels for 5700 MultiTechnique spectrometer with monochro- the sesquitelluride and oxide [8,9]. The intensity of matic Al Ka irradiation ðhn ¼ 1486:6eVÞ as an Ga 3d emission also was not instantly changed, excitation source. The spectrometer was calibrated which points out the redistribution of gallium with respect to the binding energy of the 4f level of between reactant and oxidation products. Much gold ðEbðAu4f7=2Þ¼84:00 eV) and the scan step was more informative are oxygen and tellurium core 0:05 eV. The oxidation was observed by measuring levels. Due to adsorption, the oxygen was detected the binding energies of gallium, oxygen and tell- in the freshly air-cleaved sample (Fig. 1a). The urium core levels. CL was excited at liquid nitrogen intensities of O 1s emission, corresponding to temperature ð77 KÞ by electron pulses with the gallium oxide (at 530.95 eV) and tellurium oxide frequency and duration of 20 Hz and 3 ms, respec- (at 531.75 eV) practically coincide with the Ga2Te3 tively. The electron beam was characterised by the stoichometry, which proves the equal quantity of density of current of 100 mA=cm2 and 9 keV chemisorbed oxygen on the surface both by gallium electron energies. Luminescence spectra in the range and tellurium. The oxidation increases the intensity of 1.2–4.2 eV were recorded using a photomultiplier of O 1s emission with simultaneous redistribution of through a monochromator. The XRD spectra of the Te–O bonds (Fig. 1b). The band, attributed to samples were recorded using CuÀKa X-ray source Ga–O bonds is much more intense than the one on DRON-4 spectrometer in the range of corresponding to tellurium oxide. The band at 10o2Yo90 with a scan step of 0:05. 533.75 eV can be connected with hydroxide groups [7], adsorbed from ambient. The most sensitive to 3. Results and discussion chemical bonds switching seemed to be a doublet of Te 3d. Evolution of chemical shifts of Te3d5=2 line XPS patterns of initial and thermally oxidized correlates well with shifts of oxygen 1s. The during 5 min at 650 1CGa2Te3 are presented in spectrum of initial sample consists of components Fig. 1. The spectral position of Ga 3d level characteristic for tellurium (IV) oxide (at 576.55 eV) Fig. 1. Detailed XPS scans of initial Ga2Te3 (a) and thermally oxidized during 5 min at 650 1C (b). Download English Version: https://daneshyari.com/en/article/730023 Download Persian Version: https://daneshyari.com/article/730023 Daneshyari.com.