Abstract :
The N-for-As, P-for-As and Sb-for-As anion exchange reactions at GaAs surfaces, and the N-for-P anion exchange reaction at
the GaP surface have been investigated with the aim at the formation of a thin high-gap surface layer for passivation of GaAs and
GaP. Among the investigated anion exchange reactions, the P-for-As results in the formation of a ternary alloys GaPyAs1 y not
effective for GaAs passivation. The Sb-for-As anion exchange does not occur and results in segregation of Sb at the GaAs
surface. The Sb overlayer is effective in the chemical passivation of GaAs. The N-for-As anion exchange by a remote N2–H2 (a
mixture of 97% N2–3% H2) radiofrequency plasma nitridation procedure forms a very thin ( 5 A° ) GaN layer that is successful
in the electronic and chemical passivation of GaAs(1 0 0) surfaces. The N2–H2 (a mixture of 97% N2–3% H2) nitridation has
been found completely different from the pure N2 nitridation which, in contrast, do not provide GaAs passivation, because the
formation of Ga–N bonds accompanies with AsN and the segregation of elemental As at the GaN/GaAs interface. GaAs–GaN
based Schottky structures have also been deposited and characterized by I–V measurements. A chemical and kinetic mechanism
for the anion exchange reactions which takes into account also the competitive formation of PAs, AsN, and PN isoelectronic
compounds is proposed.
