Band Alignment of n- and p- InP at Electrolyte and Ultra High Vacuum Intrefaces: Correlation between the Open Circuit Potential under Illumination and XPS Photopeak Energy Separations

Abstract

This paper describes some fundamental concepts of Fermi level equalization between InP (n- and p- types) and two contrasted surface configurations: the liquid interaction on the one hand and the ultra high vacuum on the other. At open circuit potential, the junction InP / liquid was gradually illuminated according to the luminous flux. A decrease of the band bending was observed for both types using n & p photopotentials in acidic aqueous electrolyte. A quasi saturation of the difference was observed for sufficient light intensities. Despite strongly different surface conditions, the evolution of the band alignment of n- and p- doped InP toward electrolyte gives rise to a difference between the open circuit potential under illumination which is very close to the peaks positions separation observed in ultra high vacuum for XPS measurements. These observations allow comparison of the different band bending configurations of n & p-InP surfaces in liquid and in vacuum.