Effect of Weakly Correlated Crystallizations in Thermically Two-Step or Three-Step Heteroepitaxial Growth

The thermically two-step and three-step growth methods have been widely used as a kind of effective method for the silicon-based heteroepitaxial growth of III–V semiconductor materials. The two-step growth method means that a low-temperature (LT) growth step and a high-temperature (HT) growth one are arranged successively; while, for the three-step growth method, one additional intermediate-temperature (IT) growth step is inserted between the LT and the HT ones. However, the concrete mechanism which leads to the improvement of the epilayer crystalline-quality in this kind of growths remains poorly understood. In this paper, a special mechanism, called as the effect of weakly correlated crystallizations (WCC effect), is proposed to provide a reasonable interpretation of the growth improvement. The validity of the mechanism has been proven by specially designed two-step molecular beam epitaxy (MBE) growths as well as three-step metal–organic chemical vapor deposition (MOCVD) growths. And, based on this new understanding, rather high quality three-step MOCVD growths, especially the thermal-cycle-annealing assisted ones, have been experimentally achieved. The low threading dislocation densities, typically as 1.8 × 106 cm–2, have been steadily demonstrated. It is believed that after further optimizations, the WCC effect based three-step growth method would play a more important role for future high-quality III–V/Si heteroepitaxial growths and relevant high-performance device fabrications.