SHALLOW DONORS AND DEEP LEVELS IN GAAS GROWN BY ATOMIC LAYER MOLECULAR-BEAM EPITAXY

We correlate the Si concentration measured by secondary ion mass spect rometry (SIMS) and the net donor concentration in GaAs:Si grown by ato mic layer molecular beam epitaxy (ALMBE); Si was supplied during: (a) both the As and the Ga subcycles, (b) the As subcycle, and (c) the Ga subcycle; the layers were grown at temperatures in the 300-530 degrees C range. The results show that Si incorporation and its compensation depend on the Si-supply scheme and that the extent of compensation dec reases with the growth temperature. We also study the deep levels in t he ALMBE GaAs grown under the above conditions. Our results show the o ccurrence of M1, M3 and M4 levels with concentrations that are: (i) es sentially independent of both the Si supply scheme and the ALMBE growt h temperature, (ii) close to those of MBE GaAs grown at 600 degrees C, and (iii) up to 2 orders of magnitude lower than that of GaAs prepare d by molecular beam epitaxy (MBE) at similar temperatures.