THERMAL-DESORPTION OF GALLIUMCHLORIDE ADSORBED ON GAAS (100)

Adsorption and desorption of galliumchloride (GaCl) on GaAs surfaces are investigated to understand the self-limiting process in the chloride atomic layer epitaxy (ALE). Adsorption energy of GaCl on GaAs (100) surfaces is determined by temperature programmed desorption (TPD). As stabilized 2 x 4 surfaces and Ga stabilized 4 x 6 reconstructed surfaces are exposed to a GaCl molecular beam which is produced by a newly designed GaCl cell. GaCl desorption is observed on both 2 x 4 and 4 x 6 surfaces, while the desorption of GaCl(x) (x = 2, 3), AsCl(x) (x = 1 approximately 3) and Cl2 are not detected. The adsorption energy of GaCl, E(ad), is calculated to be 38 kcal/mol for the 2 x 4 surface and 32 kcal/mol for the 4 x 6 surface. The adsorbed species in chloride ALE process is also discussed with reference to the surface residence time of GaCl.