방사광 가속기를 이용한 (NH4)2Sx 처리 AlGaAs 표면의 X-선 광전자A 분석 연구

Abstract

Atomic bonding states of the surface of (NH₄)₂S_x-treated AlGaAs and their change with annealing temperature were investigated by synchrotron radiation photoemission spectroscopy. The surface of AlGaAs sample was passivated using (NH₄)₂S_x solution after the removal of native oxide by NH₄OH solution. This (NH₄)₄S_x passivation was effective in removing Ga-O and As-O bondings, and resulted in the formation of Ga-S, As-S and Al-S bondings. Sulfur atoms migrated from As and Ga to Al atoms when the sample was annealed in ultra-high vacuum. The valence band spectra for the (NH₄)₂S_x treated AlGaAs surface showed that the Fermi level shifted by 0.21 eV after annealing at 550℃. This resulted from the increase of Ga or Al vacancies which energy states located near the valence band maximum.