Heteroepitaxial Mechanism of Ouantum-Effect Semiconductors

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We have investigated the heteropitaxial mechanism of GaAs/InAs/GaAs self-assembled quantum structure by using atomic force microscopy (AFM), high resolution transmission electron microscopy (HR-TEM), and photoluminescence measurement. For multi-stacked GaAs/InAs/GaAs structure, 1) 100A-thick GaAs layr is required to embed the InAs dots, 2) InAs quantum dots are formed on the InAs dots exist under the GaAs barrier layrs, 3) luminescence due to higher quantum-level in the InAs quantum dots can be observed under the high excitation condition. Initial stage of GaInN/GaN heteroepitaxy also investigated to achieve an nitride based quantum-dots. From the theoretical approach, strain distribution and transition thickness of 2D to 3D transition for self-assembled quantum dots are carried out by using numerical calculation based on the valence-force-field model. We have successfully obtained a general law of transition thickness by analytical approach.