Gradual Evolution From Quantum‐Well‐Like to Quantum‐Dot‐Like Characteristics in InGaAs/GaAs Nanostructures

Dense arrays of carrier localizing indium‐rich regions (referred to as quantum well‐dots, QWDs) formed inside an indium‐depleted residual quantum well by metalorganic vapor phase epitaxial deposition of 4–16 monolayers (ML) of InxGa1−xAs (0.3 < x < 0.5) on 6° misoriented GaAs (100) substrates are studied. It is shown that in addition to QWDs the deposited layers may contain other objects with size and shape similar to conventional self‐organized quantum dots (QDs). Transmission electron microscopy and photoluminescence studies reveal that the density of QDs grows with the increase in indium composition and average amount of deposited InGaAs. The QWDs show efficient absorption in the optical region of 900–1100 nm, whereas QDs do not contribute to photocurrent spectra and result in a waste of carriers. Optimal indium composition x to form QWDs with high structural and optical quality is about 0.4. For x = 0.3 the QWDs are not yet well developed, while for x = 0.5 the density of QDs becomes too high.