IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Semiconductors Monday Sessions
       Session SC+SS-MoA

Paper SC+SS-MoA3
Study of GaAs(100) Surface Cleaning Using Synchrotron Radiation Photoemission Spectroscopy

Monday, October 29, 2001, 2:40 pm, Room 122

Session: Semiconductor Surfaces
Presenter: Z. Liu, Stanford University
Authors: Z. Liu, Stanford University
Y Sun, Stanford University
F. Machuca, Stanford University
W.E. Spicer, Stanford Synchrotron Radiation Lab
P. Pianetta, Stanford Synchrotron Radiation Lab
R.F.W. Pease, Stanford University
Correspondent: Click to Email
Atomic surface cleanliness is required for novel NEA electron emission devices fabricated from GaAs and is also very important for GaAs MBE growth. Chemical cleaning of the GaAs (100) surface has been studied with high-resolution photoemission spectroscopy using synchrotron radiation (in the range of 55 eV to 750 eV) at the Stanford Synchrotron Radiation Laboratory. The high surface sensitivity of the technique has allowed us to identify the chemical state of the surface species after both the chemical cleaning and final vacuum processing steps. In order to eliminate contamination from the surroundings, all chemical cleaning steps were performed in an Ar or N@sub 2@ purged glove box attached to the load-lock allowing samples to be transferred into the system without being exposed to air. Samples were etched in H@sub 2@SO@sub 4@:H@sub 2@O@sub 2@:H@sub 2@O solution and then heat cleaned at 500°C (both diluted and concentrated solutions were studied). After chemical etching in the dilute (4:1:100) solution, elemental As (>1ML), As sub oxide (~0.1ML), Ga sub oxide and C (0.5~1ML) are found on the surface. Subsequent annealing at 500°C in UHV produces a stoichiometric, oxide free surface as determined by valence band and core level photoemission. In addition, C has been reduced to less than 10% of its initial level. We believe that the C can be removed by heating because the elemental As from the earlier cleaning step tends to protect the GaAs surface.