The Geometric Structure and Electronic Properties of the Potassium/gallium ARSENIDE(110) Interface
Abstract
A study of the K/GaAs(110) interface has been undertaken to explore the initial stages of metal-semiconductor interface development. Several experimental techniques were utilized in this study to probe alkali-metal induced structural modifications of the GaAs(110) surface and the evolution of the electronic properties of the interface. These include TDS, DeltaPhi, LEED, and EELS. STM and ARPES data from other workers were compared to the data obtained in this study to establish a unified picture of the interface. TDS revealed that K forms a saturation layer at a coverage defined as Theta_{sat} for deposition at 300 K. LEED background intensity analysis as a function of coverage indicated that there is no long-range ordering of the K overlayer at any coverage up to Theta_ {sat}. Preferential attenuation of multiple scattering peaks at partial K coverages permitted a kinematic LEED intensity analysis of diffraction from the underlying GaAs substrate as a function of adsorbate coverage. The results of this analysis show that the clean GaAs(110) relaxation is removed by ~1/2 Theta_{sat} at 300 K. Electronic excitation spectra of the developing interface obtained with EELS revealed a continuous narrowing of the interface band gap for increasing K coverage reaching ~200 meV at Theta _{sat}. Finite excitation intensity within the gap at room temperature was quenched at low temperatures. This effect is consistent with thermal excitations across a true interfacial band gap. An apparent contradiction between the value of the energy gap as measured by EELS and ARPES has been reconciled by considering electron correlation effects within the interfacial layer. For deposition beyond Theta_{sat}, obtained by deposition onto a room temperature saturated surface which had been cooled to ~ 135 K, the excitation spectra showed that the semiconductor to metal transition occurs at ~1.2 Theta_{sat}. Rapid metallization of the interface for deposition of K onto the clean GaAs(110) substrate held at ~ 135 K indicates that the growth mode at low temperature is distinctly different from that at room temperature.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- February 1991
- Bibcode:
- 1991PhDT........61V
- Keywords:
-
- POTASSIUM/GALLIUM ARSENIDE(110);
- Physics: Condensed Matter