Ambient scanning tunneling spectroscopy of n- and p-type gallium arsenide

Ambient scanning tunneling spectroscopy (STS) of n- and p-doped GaAs (110) and (100) surfaces, prepared with a stable, electrically transparent surface oxide, reveals that the current-voltage (I-V) characteristics of these surfaces are essentially identical to the I-V properties of the free (110) surface cleaved in ultrahigh vacuum. These results demonstrate for the first time that: (1) meaningful STS spectra of GaAs surfaces can be obtained in air, (2) the passivating layer, consisting of a stable, ultrathin oxide [J. A. Dagata, W. Tseng, J. Bennett, J. Schneir, and H. H. Harary, Appl. Phys. Lett. 59, 3288 (1991)], allows the scanning tunneling microscopy tip to probe the bulk electrical properties of the semiconductor, and (3) quantitative doping information, 1015