IODINE USE IN SOLID-SOURCE ILL-V MOLECULAR-BEAM EPITAXY

Use of iodine for in situ etching of GaAs, AlAs, and InAs in solid-sou rce molecular-beam epitaxy has been explored. Reflectance high-energy electron-diffraction intensity oscillations have been observed during iodine etching of GaAs and InAs, indicating a molecular layer-by-layer nature of material removal. Etch rates of GaAs and InAs determined fr om the period of the oscillations are comparable for a given iodine fl ux. Secondary-ion-mass spectroscopy depth profiles indicate that the e tching of AlAs is negligible, and that iodine can be used as a selecti ve etch which stops on AlAs or AlGaAs layers. Electrical properties of GaAs layers grown with an iodine beam impinging on the surface are co mparable to those of the layers grown without iodine. Use of iodine fo r the surface cleaning of GaAs has also been examined. Our results sho w that iodine etching prior to growth reduces the level of carbon cont amination at the substrate epilayer interface. (C) 1996 American Insti tute of Physics.