Growth of Thick Epitaxial CdTe Films by Close Space Sublimation

Abstract

This paper reports on a detailed study of the development of the close space sublimation method, which has been widely used in the preparation of polycrystalline CdTe/CdS solar cells, as an epitaxial method for the growth of thick CdTe single crystal films over 200 lm on GaAs and Ge substrates for highenergy radiation detectors. The resulting microscopic growth phenomena in the process are also discussed in this paper. High-quality single crystalline CdTe thick films were prepared with x-ray rocking curves full width at half maximum (FWHM) values, which were $100 arcsec on Ge substrates and 300 arcsec on GaAs substrates. The quality of thick films on Ge(100) showed a substantial improvement with nucleation in a Te-rich growth environment. No Te inclusions in the CdTe films grown on GaAs(211)B and Ge(100) were observed with IR transmission imaging. Photoluminescence of CdTe/Ge shows a large reduction in the 1.44 eV defect energy bands compared with films grown on GaAs substrates. The film resistivity is on the order of 10 10 X cm, and the film displayed some sensitivity to alpha particles.

Optimizing diode thickness for thin-film solid state thermal neutron detectors

“…Although the thickness is quite high, the authors report the film is sensitive to alpha particles. 12 We utilized the publicly available Monte Carlo based computer modeling programs MCNP5 and MCNPX v2.7.0 to simulate neutron, charged particle and photon/electron transport. Our primary tool within these programs was the pulse height tally, which allows easy determination of the energy deposited in a material volume by incident charged particles and photons.…”

Surface and interface of epitaxial CdTe film on CdS buffered van der Waals mica substrate

“…Literature reports that the FWHM of rocking curve of CdTe(001) film grown by close space sublimation on 6 o mis-oriented Ge(001) substrate decreases as the film thickness increases. For a 2 µm thick CdTe film on Ge(001) the rocking curve is ~0.3 o[5]. Our 2.6 o is from CdTe(111) film on epitaxial CdS(0001) film that is much broader than 0.3 o but the rocking curve spread could be reduced by growing a thicker CdTe film.…”

“…One of the most important strategies to create high crystallinity films is to grow them epitaxially on single crystal substrates. The techniques used to grow CdTe films are rich, including but not limited to molecular beam epitaxy [1,2], e-beam evaporation [3], hot wall epitaxy [4], close space sublimation [5], high vacuum evaporation [6], chemical bath deposition [7], and metalorganic chemical vapor deposition [8]. Examples of single crystal substrates used are Si [2,4,9,10], Ge [1,3,5,8,11], CdTe [12,13], CdS [12,14], GaAs [8,[15][16][17][18][19][20][21], Al 2 O 3 [22], and SrTiO 3 [23].…”

Cadmium telluride semiconductor detector for improved spatial and energy resolution radioisotopic imaging

“…[ 46 ]-Meanwhile, a proper epitaxial growth technique for providing single crystalline thick fil with the following properties was used: (1) a growth rate ranged from 1 to about 100 μm/h; (2) uniformity formation and steady temperature growth, to make homogeneity and perfectly, freeness from defects that would strictly decline the device's performance; (3) the source materials shall be economical in the market. [ 47 ] The growth of a flat crystal with a large area has already been a challenging job. [ 48 ] The epitaxial growth of a thick CdTe layer on great-area substrates, for instance, GaAs or Si, is a favorable way to provide the large-area detectors.…”

“…Meanwhile, appropriate methods for thin-film deposition are commercially possible. [ 17 45 47 49 51 ]…”