Quantum Dot Devices

In Section 5.1, we defined the ideal 1DES and introduced realistic1DESs that can be fabricated from various types of semiconductors.If the free electron motion in a 1DES is frozen by further confine-ment in the z-direction (the direction in which electrons freely move in the 1DES), then the system is called a zero-dimensional electronsystem (0DES). Figure 6.1 shows a conceptual diagram of a 0DES. Itis basically the ideal 1DES of Fig. 5.1 with two walls added to thefigure to denote the potential confinement, blocking electron mo-tion in the z-direction. Electrons are captured between the potential walls and cannot move freely even in the z-direction. The only way for the electrons between the two walls to be released is either byquantummechanical tunneling through thewalls or by jumping overthe walls. Classically, the most important energy that these 0DESelectrons have is the electrostatic energy determined by the totalcharge (the self potential energy) and the electrostatic potential ofthe system (the external potential energy).