Explanation

It refers to a potential well with discrete energy values. Generally, the potential well of electrons or holes with obvious quantum confinemem effect formed by the interphase arrangement of two different semiconductor materials. Due to the limitation of quantum well width (quantum well can be formed only when the well width scale is sufficient), the carrier wave function is localized in the one-dimensional direction. Because the thickness of the active layer in the quantum well is only within the mean free path of electrons, the well wall has a strong restriction effect, making the carrier only have two-dimensional degree of freedom in the plane parallel to the well wall. In the vertical direction, the conduction band and the valence band are split into subbands. To form quantization, particles that can move in three-dimensional space A can be bound to a planar region. In a quantum well with a two-dimensional degree of freedom, the relationship between the density of states of electrons and holes and energy is a step shape, unlike the parabolic shape of a three-dimensional materials. Multiple quantum well are multilayer structures formed by the alternate growth of two different semiconductor materials. If the barrier layer is thick enough, so that the coupling between the carrier wave functions between adjacent potential wells is very small, the multilayer structure will form many separate quantum well, called multiple quantum well (MQW). The preparation of quantum well is usually formed by clamping a materials between two materials (usually wide band gap materials), such as gallium arsenide sandwiched between two layers of aluminum arsenide. Generally, this materials is prepared by MBE (molecular beam epitaxy) or MOCVD (chemical vapor deposition).

Classification