Nanostructured surfaces

Development and investigation of InAs, GaAs, InSb, GaSb polished surface
Levchenko I.V.1,2, Tomashyk V.M.1, Malanych H.P.1, Stratiychuk I.B.1
1 Semiconductor Chemistry Department, Institute of Semiconductor Physics of the NAS of Ukraine. Prospect Nauki, 41, Kyiv-03028, Ukraine. 
E-mail: irynavlevchenko@gmail.com
2 Optoelectronic Devices Laboratory, Institute of High Pressure Physics of PAS. 29/37 Sokolowska St., Warsaw-01142, Poland.

III-V semiconductor crystals are considered for applications as materials for photodetectors, high electron mobility and heterojunction bipolar transistors, resonant tunneling diodes, spintronic devices solar cells, and so on.
Two mechanisms of the wet treatment of substrates have been proposed to account for features of the InAs (001), GaAs (111), InSb (112), GaSb (112) dissolution process in the (NH4)2Cr2O7–HBr–EG etching solutions.
The crystal treatment included next stages: mechanical grinding, chemical-mechanical polishing (CMP) and chemical-dynamic polishing (CDP). In-process washing of crystals was carried out after every treatment stages in Na2S2O3 and NaOH solutions and distilled water. According to the grain abrasive diameter, the removal speed of the damaged layer was 11-31 μm/min. Mechanical grinding decreases the thickness of the damaged layer from 150 μm (after cutting) to 10-22 μm. CMP was carried out on the glass polisher. The procedure was performed by the non-abrasive etching solution. CDP was the finish stage of the substrate modification. It was carried out in the reproducible hydrodynamic conditions using the disk rotation method. For CDP process, the etching rate was 0.1-8.4 μm/min. Replacement of the polishing process type from CDP to CMP promotes the increase of dissolution rate. Mechanical influence of CMP and variation of the etchant composition increase the etching rate from 0.1 to 57 μm/min.
Two types of the crystal surface morphology: polished and covered by the film were studied. Saturated by solvent etchants formed the clean and defect-free surface after CDP and/or CMP. Solutions with high concentration of the oxidant produced unpolished surface morphology. In the polished etchants both CDP and CMP procedures lead to the formation of the mirror-like and super-smooth surface with roughness less than 1 nm.
However, CPM treatment causes the more homogeneous surface of the InAs, GaAs, InSb, GaSb semiconductors, in comparison with CDP.