Efficient electron-stimulated desorption of hydrogen from GaN(0001)

Electron-stimulated desorption (ESD) of hydrogen from GaN(0001) has been ob served and characterized using electron-energy-loss spectroscopy. Auger ele ctron spectroscopy and low-energy electron diffraction show that the GaN su rface is clean but faceted.: As previously reported, saturation exposure to atomic hydrogen produces a decrease in the intensity of energy-loss peaks at 3.5 and 6.6 eV and an increase in the intensity of loss peaks at 11.7 an d 18 eV. Bombardment with 90 eV electrons produces a reversal of the hydrog en-induced changes at 3.5, 6.6, and 11.7 eV. The increased intensity at 18 eV is almost unchanged by electron exposure. We conclude that the reversal of changes at 3.5, 6.6, and 11.7 eV is due to electron-stimulated desorptio n of hydrogen from Ga sites while the loss peak at 18 eV is due to bulk hyd rogen and not affected by 90 eV electrons. Cross sections for removal of H and D are found to be (2+/-1)x10(-17) and (7 +/- 3)x10(-18) cm(2), respecti vely. The large cross section and small isotope effect for ESD of hydrogen from GaN indicates the participation of a long-lived excited electronic sta te. [S0163-1829(99)13931-6].