The Development of BEEM Modeling for the Characterization of Si/Ge Self-Assembled Quantum Dot Heterostructures

In this paper we present a ballistic electron emission microscopy (BEEM) modeling for the Si/Ge quantum dots characterization. BEEM is a new characterization technique by using electrons ejected from the scanning tunneling microscopy (STM) tip to investigate the metal-semiconductor interfaces. Because of the high resolution of the STM system, BEEM is promising in the characterization of quantum dots as the charge transport on individual dot can be characterized compared to the multitude of dots necessitated in other techniques. This method requires three terminals: a connection to the STM tip to inject electrons, a connection to the sample to collect electrons that traverse the interface, and a third grounding terminal. The energy and angular distribution of the injected electrons can be controlled by varying the tip potential. By using the characteristic data of the injected and collected electrons, many useful transport-related properties of the sample can be obtained. The silicon quantum dots (Si QDs) may be fabricated by taking advantage of the Stranski-Krastanov growth model. Germanium layer has been choosed as a barrier layer due to the large lattice mismatch between Si and Ge. The n-type Si