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Surface Cleaning of Si-Doped/Undoped GaAs Substrates

It was found that the surface morphology and residual impurities after substrate-cleaning processes are influenced by the existence of a Si dopant in a GaAs (001) substrate. Atomic-force microscopy observations have revealed that the surface of an undoped substrate after conventional thermal cleaning under an As4 flux is smoother than that of a Si-doped substrate. The surface roughness of Si-doped substrates was greatly improved by cleaning using hydrogen radicals ( H•). Furthermore, secondary ion mass spectrometry revealed that the concentrations of residual carbon and oxygen on a H•-cleaned surface were also markedly reduced on undoped substrates, compared to those on Si-doped substrates.