Single Crystalline Quantum Films and Superlattices

Quantum films are usually produced in a periodic sequence of sandwich type of two semiconductors, one with a small, the other with a large bandgap, as illustrated in Fig. 9.7a. They can be produced with much higher precision than quantum dots of a narrow 

Quantum films represent a beautiful physical example of the particle in the box problem. The energy levels of the conduction band electrons in the electron well (MQW) can be easily calculated using the envelope function or the effective mass approximation [6]. The electron wave function is then [29-31] 

The calculation of hole levels is much more complicated because the band structure of most semiconductors shows hole bands of fourfold degeneracy at /c = 0. This leads to light and heavy holes with different effective masses (see Section 1.2). Consequently, a double set of energy levels is formed in a quantum well. 

A further theoretical analysis of the quantum film shows that the density of states (DOS) is given by [2] 

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