ETCHING OF INP(100) 4X2 AND MOLECULAR-BEAM EPITAXIALLY GROWN GAAS(100)-C(4X4) WITH ATOMIC-HYDROGEN

Phonon, plasmon, and vibrational modes of clean and hydrogenated molec ular-beam epitaxially grown As-rich GaAs(100)-c(4 X 4) and ion-bombard ed and annealed InP(100) 4 X 2 have been studied with high-resolution electron energy-loss spectroscopy. The plasmon energy at the interface of depletion layer and bulk enabled us to determine the carrier conce ntration for Si-doped GaAs samples. With increasing hydrogen exposure characteristic changes in plasmon energy, its intensity and the intens ity of the surface optical phonons have been observed. This is explain ed by changes in the space charge regime. Using hydrogen as a local pr obe provides sensitivity to the stoichiometry and to the chemical bond ing situation at the uppermost surface layer. It is shown that the As- terminated GaAs(100) surface can be converted finally into a Ga-termin ated surface by etching with atomic hydrogen. For InP, for the very fi rst time an interface plasmon was observed at 90 meV, due to high S do ping. In contrast to GaAs, sequential hydrogenation results in the for mation of metallic droplets (In), which increase in size and concentra tion with increasing hydrogen exposure. Consequently, the phonon and p lasmon intensities are reduced drastically. Models of the atomic surfa ce structures for different stages of hydrogenation are discussed.