OBSERVATION OF A NEW CUPT-TYPE ORDERED-PHASE WITH ORIENTATION IN THE [111]A DIRECTION IN AL0.5IN0.5P ALLOY

A new type of CuPt ordered-phase (CuPt-A) with orientation in the [111 ]A and [($) over bar 1 ($) over bar 11]A directions was found in Al0.5 In0.5P grown at 520 degrees C on exact (001)GaAs substrate by gas-sour ce molecular-beam epitaxy. Weak formation of conventional CuPt-B type ordered phase was also obs erved in the same AlInP layer. The surface reconstruction observed by RHEED during the growth was (2 x 2). At a g rowth temperature of 560 degrees C the surface reconstruction was (2 x 1) and only conventional CuPt-B was formed. A step array parallel to [110] and descending towards [($) over bar 110] was found to promote f ormation of the CuPt [111]A variant.