EPITAXIAL GROWTH AND CHARACTERIZATION OF HIGH QUALITY CdTe (111) VIA CLOSED-SPACE SUBLIMATION A. Escobedo, J.C. McClure, D. Zubia University of Texas El

EPITAXIAL GROWTH AND CHARACTERIZATION OF HIGH QUALITY CdTe (111) VIA CLOSED-SPACE SUBLIMATION

A. Escobedo, J.C. McClure, D. Zubia University of Texas El Paso DMR-0521650

Epitaxial growth of CdTe using close-spaced sublimation (CSS) was performed to produce high quality epitaxial smooth films on CdTe (111) substrates. The epitaxial growth is achieved with a CdTe single crystal as the source. Special interest in using CSS versus conventional molecular beam epitaxy (MBE) is due to lower cost and faster growth rates. To achieve the project goal, two studies were performed to better understand the CSS technology applied to this system andthe behavior of the CdTe (111) substrates under different conditions.The depositions consisted of heating the CdTe (111) substrates at different temperatures inside the CSS with a glass slide as a “blank source” to measure the amount of sublimed material at these temperatures. This study was performed to determine the threshold temperature for sublimation and the temperature needed to produce a usable growth rate of 1μm/hr. Figure 1 summarizes this set ofexperiments. Fig 1



After the sublimation study was completed, the temperatures selected for the first deposition were 350oC for the substrate to avoid sample sublimation and 480oC for the source to have a growth rate of about 1μm/hr. A new set of experiments was then performed by increasing the source temperature in steps of 10 degrees up to 530oC. The substrate was kept at the same nominal temperature but the source temperatures had a slight effect on the substrate temperatures due to system limitation. Therefore, the substrate temperature increased in each of these new experiments but maintained a nearly constant temperature difference of 130oC. Also, as an additional experiment, a post deposition anneal was performed on the sample with substrate and source temperatures of 350oC and 480oC.

The films were characterized by profilometry, scanning electron microscopy (SEM recently purchased through NSF grant DMR-0521650), electron backscattering diffraction (EBSD), and x-ray diffraction (XRD). In particular, SEM showed that the films are very smooth with grains coalescing nicely. Furthermore, EBSD and XRD rocking curves demonstrated highly oriented films in the (111) direction Moreover, from SEM, XRD and EBSD data the post-annealing process increases crystal quality. In summary, all characterization results indicate that our goal has been substantially achieved.



-520 sample at 5kx 385-520 sample at 20kx

350-480 sample at 5kx after annealing350-480 sample at 5kx before annealing



X-ray Rocking Curves for Some of the Samples. Note that post deposition anneal substantially narrowed the curve.

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EPITAXIAL GROWTH AND CHARACTERIZATION OF HIGH QUALITY CdTe (111) VIA CLOSED-SPACE SUBLIMATION A. Escobedo, J.C. McClure, D. Zubia University of Texas El