This work presents the AlGaAs and GaAs etching results using a RIE reactor and SiCl4/Ar plasma. These materials can be applied in HEMT devices fabrication. The influence of the process temperature on etch rates has been studied. Selectivity of etching and the importance of the periodical process chamber cleaning for SiCl4 containing gas mixtures are discussed. For optimized conditions, GaAs etch rate as high as ∼50nm/min with low surface roughness, for process duration as long as 60 min, have been obtained. © The Electrochemical Society.91169177Lee, J.W., Jeon, M.H., Cho, G.S., Yim, H.C., Chang, S.K., Kim, K.K., Devre, M., Pearton, S.J., Development of advanced plasma process with an optical emission spectroscopy-based end-point technique for etching of AlGaAs over GaAs in manufacture of heterojunction bipolar transistors (2002) Solid-State Electronics, 46, pp. 773-775Lee, J.W., Jeon, M.H., Devre, M., Mackenzie, K.D., Johnson, D., Sasserath, J.N., Pearton, S.J., Shul, R.J., Understanding of etch mechanism and etch depth distibution in inductively coupled plasma etching of GaAs (2001) Solid-State Electronics, 45, pp. 1683-1686Mestanza, S.N.M., Frateschi, N.C., Electron cyclotron plasma etching damage investigated by InGaAs/GaAs quantum well photoluminescence (2006) J. Vac. Sci. Technol. B, 24 (6), pp. 2726-2730Giehl, A.R., Gumbel, M., Kessler, M., Herhammer, N., Hoffmann, G., Fouckhardt, H., Deep dry etching of GaAs and GaSb using Cl2/Ar plasma discharges (2003) J. Vac. Sci. Technol. B, 21 (6), pp. 2393-2397Dultsev, F.N., Nenasheva, L.A., The effect of hydrogen as an additive in reactive ion etching of GaAs for obtaining polished surface (2006) Appl. Surf. Sci, 253, pp. 1287-1290Choquette, K.D., Shul, R.J., Howard, A.J., Rieger, D.J., Smooth reactive ion etching of GaAs using a hydrogen plasma pretreatment (1995) J. Vac. Sci. Technol. B, 13 (1), pp. 40-42