Self-masking selective epitaxy by molecular-beam method

Using collimated Ga and As4 molecular beams from limited-source apertures, epitaxial GaAs layers were grown selectively by self-masking on preferentially etched GaAs surfaces with a lateral accuracy of 0.1 μm. From edge profile analysis, it is found that (1) the accuracy is limited by preferential growth of an obstruction layer, (2) the surface diffusion length of free Ga is dependent upon As4 arrival rate, and furthermore (3) the length is less than 200 Å in As-rich growth conditions, while in Ga-rich conditions the length is 1900 Å.