My lab is working with a ZnTe MBE film grown on GaSb. We etch of the GaSb substrate, but find (via Raman) Te on the remaining ZnTe-film surface. It is difficult to remove. Does anyone know what might dissolve/etch it away without damage to the ZnTe?
As far as I know, Te does not dissolve easily in any "normal" solvent.
Did you try to heat the film so as to evaporate the extra Te?
Te, containing compounds like ZnTe and CdTe suffer from this problem. Whatever the growth technique used, Te tend to precipitate within the material or deposit as elemental Te on the surface. Please refer to my work published in:
Appl. Phys. Lett. 1989, 54(2) p137. and Appl. Phys. Lett. 1988, 53(26) pp2623-2625.
Surface Te can be removed by Alkaline solutions. These solutions temove Te preferentially from bulk CdTe leaving Cd-rich surface.
Acidic etchants preferentially remove Cd, and leave a Te-rich surface. We saw this trend is common for CdTe, CdS and ZnSe. ZnTe behaviour should be similar.
Please also refer to the review paper:
Progress in Crystal Growth and Characterisation. Vol. 36, No. 4. (1998) pp 249-290.
Good Luck.
Dharme.
Thank you to Drs. Yannopoulos and Dharmadasa for these replies. We are following up on your suggestions. Annealing the film at 250 C in a nitrogen atmosphere produced a stronger Te Raman signal.
Producing a stronger Te Raman signal shows that improvement of the crystallisation of the Te layer present on annealing. Perhaps you need to anneal at a higher temperature to sublime Te layer. This temperature should not decompose ZnTe and may need a careful optimisation.
If Te precipitates are embedded in ZnTe layer, Te could vaporise during annealing. This will create holes in the ZnTe layer. We observe this in CdTe all the time. Please try the etching I suggested, but this will only remove surface Te layers. Embedded Te-precipates will remain.
Good Luck! Dharme.
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