INVESTIGATION OF INAS SUBMONOLAYER AND MONOLAYER STRUCTURES ON GAAS(100) AND (311) SUBSTRATES

We demonstrate a new route to the synthesis of InAs monolayer structur es in GaAs by bridging the fundamental gap between the requirement of the lowest possible substrate temperatures to suppress In segregation and the necessity to maintain sufficiently high temperatures for the g rowth of low-defect density material. This mediation between opposing aspects of the molecular beam epitaxy of these InAs structures is achi eved by a modulation of the substrate temperature and by a minimizatio n of the amount of GaAs cap material grown at low temperature. High-re solution x-ray diffraction and high-resolution electron microscopy com bined with photoluminescence (PL) and PL excitation spectroscopies rev eal excellent structural properties for our series of (311) and (100) oriented submonolayer and monolayer structures. A comparison of our PL results with already published data proves our In concentration profi les to be very sharp and from a numerical analysis we deduce an upper limit of 0.2 for the In segregation probability in these structures. I n addition we obtain as upper limits for the conduction band offsets Q (c)(100) less-than-or-equal-to 0.4 and Q(c)(311) less-than-or-equal-to 0.55 for (100) and (311) orientations, respectively.