Growth mode transitions induced by hydrogen-assisted MBE on vicinal GaAs(110)

Modified energetics and growth kinetics on H-terminated GaAs (110)

“…The AFM images show a characteristic faceting of the surface with straight bunched steps along the [110] direction for all three samples. The progressive narrowing of the terrace width and tendency towards step debunching with increasing atomic H dose previously reported 16,17 can be clearly observed in these images. In addition, the rms surface roughness decreases after exposure to the atomic hydrogen beam, this effect being more pronounced when the exposure is continued during epitaxial growth.…”

Step-step interactions on GaAs (110) nanopatterns

“…These results demonstrate that the steady state is reached at an earlier stage on the H terminated surface, thus corroborating the catalytic role of H in the GaAs (110) growth process observed by RHEED. 10 In addition, the stronger step-step interactions found for this series in comparison to the series of samples grown by conventional MBE at the same temperature (set B) stem not only from the increment of entropic repulsions originated by the narrower terraces, but, most importantly, from the energetic (dipole-induced) interactions between the H-terminated ½1 12 steps. The latter becomes particularly relevant at low temperatures, where the exothermic reaction of H with the GaAs (110) surface leads to a higher H coverage of surface steps.…”

“…10,30 Under the experimental conditions specified for sample I, conventional MBE proceeds by preferential incorporation of adatoms to the more reactive ½1 10 surface steps, where stable (001) nanofacets with As-As dimers are formed by step bunching. The observed TWD thus describes mainly the effective attraction between ½1 10 steps within the (001) nanofacets, since long-range repulsive interactions between bunches, accounted for by the secondary peak, are negligible in this sample.…”

“…Previous dynamic reflective high energy electron diffraction (RHEED) studies in combination with AFM topography images have shown that, under the specified experimental conditions, bunching of ½1 10 steps occurs from the onset of growth by preferential adatom incorporation from the upper terraces in the presence of inverse E-S step edge barriers. 10,30,32 The images in Figs. 3(a) and 3(b) also evidence that in the early stages of growth the surface is unstable against step meandering, exhibiting terraces laterally bounded by ½1 1n-type step edges (n ! 2).…”

“…Experimental studies have demonstrated that the TWD can be artificially modified to fabricate surface patterns with improved lateral uniformity by exposing the surface to certain surfactant agents like atomic hydrogen that induce changes in adatom attachment kinetics during growth. 10 Theoretical attempts to determine the strength of step-step interactions from the TWD have produced different results depending on the specific approximation employed. [11][12][13][14][15] The distribution of interstep distances is the result of both step fluctuations and step-step energetic interactions.…”