COMBINED ANALYSIS OF OVERLAYER S/GAAS INTERFACES WITH PHOTOEMISSION SPECTROSCOPY AND X-RAY STANDING-WAVE/

Metal/GaAs or insulator/GaAs interfaces with a sulfur interlayer have been investigated using photoemission spectroscopy and the X-ray stand ing wave (XSW) method in order to determine the structure and chemical bonding at the interface and further correlate this with the electric al properties. It is found that while a CaF2 overlayer is not very rea ctive towards the S interlayer, deposited Al strongly reacts with the surface S-Ga layer to form a thermodynamically stable Al-S interface m onolayer, which plays a role in achieving metal-dependent Schottky con tact. On the other hand, reactive Pd metal disrupts the S-passivated G aAs surfaces, resulting in surface segregation of sulfur. In this case , the Schottky barrier heights are identical to Pd/GaAs, indicating th e importance of S remaining at the interface. XSW analysis reveals tha t the CaF, and Al/S/GaAs systems have well-ordered interfaces. Thus, t he stability of the S passivation layer is discussed in terms of the S -Ga binding energy and the reactivity of the deposited overlayer.