Properties of the CdTe/InSb Interface Studied by Optical and Surface Analytical Techniques
|Zhe C. Feng|
National Taiwan University (NTU), Roosevelt Rd., Taipei 106-17, Taiwan
The interface properties of CdTe/InSb grown by molecular beam epitaxy (MBE) and the In interdiffusion were studied by optical and surface techniques of photoluminescence (PL), Raman scattering, X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS). Correlationship between two types of investigations was established. We have the following results:
(1) The In interdiffusion was revealed directly by SIMS depth profile and XPS In 3d and 4d spectra, indicating that the In concentration in CdTe film grown with high substrate growth temperature Ts is much higher than that with low Ts. Higher Ts enhanced the In interdiffusion across the CdTe/InSb interface, leading to more indiums detected.
(2) PL spectra from two Ts samples are quite different. The low Ts one possesses strong free and acceptor-bound excitons, relatively weaker and sharp emissions in the deep level range of 1.4-1.5 eV, characteristic of high quality of single crystalline CdTe. The high Ts one has dull FE feature only and strong defect-related E and F lines and deep 1.44 eV broad band.
(3) We had varied the Ts between 170-285 C and obtain an optimum Ts of 185 C. It shows that there would exist an exact lattice match between CdTe and InSb at 185 C and that a(CdTe) > a(InSb) as T<185 C and a(CdTe) < a(InSb) as T>185 or 200 C. At higher Ts, the bigger lattice mismatch would lead to dislocations and In will diffuse more efficiently along these dislocation lines from InSb substrate into CdTe layer. The big amount of In leads to the strong signals of XPS spectra and SIMS profiles, and also to the strong In and defect-related PL and Raman features. Optimizing Ts and other growth conditions are efficient to depress the In interdiffusion during the II-VI/III-V growth.
Presentation: oral at E-MRS Fall Meeting 2005, Symposium F, by Zhe C. Feng
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-20 03:34 Revised: 2009-06-07 00:44