Metamorphic growth of various heterostructures provides a broader range of available materials for band gap engineering. The conditions for successful InAs metamorphic epitaxial lateral overgrowth of GaAs patterned by W with low-pressure metal organic vapour phase epitaxy were studied. The substrates used were GaAs (100) wafers and the range of growth temperatures between 500^oC and 600^oC and the V − III ratios in the range of 21 to 56. Various orientations of the pattern were tested. It was found that the InAs nucleates as SK-islands along the W/GaAs edge.
100-nm-wide tungsten lines, oriented in 30^o off from [011] were covered with an InAs layer. The surface was planarized after 350 nm growth of strained InAs layer. The low growth temperature and the scaling of the W pattern dimensions allowed the formation of a flat (100) surface as compared to the ridged InAs formation obtained with InAs overgrowth on SiO₂/GaAs [1]. Lines, oriented along [011] and [011]were found to effectively block the lateral overgrowth by the formation of mesa ridges limited by (111A) and (111B) facets. All other grating directions showed limited coverage of the tungsten. These results are in general agreement with homoepitaxial overgrowth directions of GaAs and InAs [2].
Electrical measurements were performed on mesa structures. Ohmic contacts are formed between the W and InAs, while Schottky contacts were still present in the W/GaAs interface. This work leads to the possibility of novel device design by including the overgrown metal layers in strained materials.
References
[1] Microstructure of lateral epitaxial overgrown InAs on (100) GaAs substrates Suryanarayanan, G.; Khandekar, A.A.; Kuech, T.F.; Babcock, S.E. Applied Physics Letters, v 83, n 10, 8 Sept. 2003, p 1977-9
[2] InAs epitaxial lateral overgrowth of W masks Wernersson, L.-E.; Lind, E.; Lembke, J.; Martinsson, B.; Seifert, W. Journal of Crystal Growth, v 280, n 1-2, 15 June 2005, p 81-6