RBS/channeling study of Er doped GaN films grown by MBE on Si(111) substrates

The influence of the Ga cell temperature on the quality of GaN films grown by MBE on p-Si(1 1 1) substrates was studied for cell temperatures (T-Ga in the range from 865 degrees C to 922 degrees C using the RES/Channeling tec hnique. The films were in situ doped during growth with Er at a constant ce ll temperature. The films show a strong dependence of the crystalline quali ty on the Ga cell temperature with the best films grown at T-Ga = 915 degre es C. For temperatures T-Ga below 880 degrees C the films showed no channel ing effect. The thickness increases linearly with the temperature suggestin g that changes in the Ga flux influence the growth process. The decrease of the Ga Bur allows the incorporation of higher Er concentrations in the fil ms. The data showed that a maximum value of about 0.35 at% was reached unde r the chosen growth conditions. The Er ions occupy mainly the Ga sublattice in the films with single crystalline quality. A comparison of the angular scans through the [0 0 1] and the (1 0 (1) over bar 1) axes with Monte Cart e simulations leads to the conclusion that a majority (similar to 90%) of t he Er ions occupies Ga sites. (C) 2000 Elsevier Science B.V. All rights res erved.