Reactivity and control of Ⅲ-Ⅴ surfaces for passivation and Schottky barrier formation

摘要

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 GaP_yAs_(1-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 N_2-H_2 (a mixture of 97% N_2-3% H_2) radiofrequency plasma nitridation procedure forms a very thin (～5 A) GaN layer that is successful in the electronic and chemical passivation of GaAs(100) surfaces. The N_2-H_2 (a mixture of 97% N_2-3% H_2) nitridation has been found completely different from the pure N_2 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.