Method for epitaxially growing GaAs thin film on Si substrate

The invention relates to a method for growing a GaAs thin film on a Si substrate in a molecular beam epitaxy manner. The method comprises the following steps of: growing a GaAs nanometer column with the thickness being 1 micron on a pretreated Si (111) substrate in an autocatalysis manner by using molecular beam epitaxy equipment; solidifying Ga drops by cooling, so that epitaxial growth of a vapor-liquid-solid (VLS) mechanism is stopped; and mainly carrying out the epitaxial growth in the lateral direction so as to form the thin film gradually; and covering the solidified Ga drops for a while, so that the GaAs thin film with a uniform and smooth surface is formed. With the adoption of the method provided by the invention, the GaAs crystal thin film with high quality is prepared on the Si (111) substrate with a cheap price. Stress between an epitaxial layer and the substrate is very small, and the dislocation at an interface position and the defect density are greatly reduced. The epitaxial growth is in-situ growth without introducing other processes, so that no external pollution impurity is introduced and the preparation process is simple.