Nombre: Franklin J. Quintero
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Nombre: Franklin J. Quintero
Scheme of the structure
TEM image of the QW (made by J. Borysiuk)
Photograph of interferences made in white light.
Interferences in 532-nm, green light.
Absorption spectra of the sample.
Photoluminescence spectrum. GaN-related peak is at 360 nm. Emission from GaInN QW is at 400 nm.
Map of intensity of the GaN peak.
Map of wavelength of the GaN peak.
FIG 1. 400 × 400 Å STM Image of the Si(001) surface at 536 K showing many small Si islands. The direction of fast monomer diffusion is parallel to the dimer rows, indicated by the black arrows.In Fig. 1 we show an image of the Si(001) surface decorated with many Si islands. Islands have grown on the upper and lower terraces with their long axes aligned perpendicular to the substrate dimer rows. According to the simple sticking anisotropy model of 1D island growth, a long 1D island should be no more likely to capture material at its ends than a short one, for both islands have just two ends. The Metiu model, however, implies that the effective end capture probability should increase linearly with length. Because the exchange mechanism transports adatoms arriving on island sides to island ends, doubling an island's length should double the rate at which material is added to its ends. A portion of one movie is shown in Fig. 2. From detailed analysis of many movie images, we found that growth is independent of length, supporting the anisotropic sticking model. One advantage of our method is that we can select and follow just the 1D islands. The simple anisotropic sticking model is therefore confirmed as the cause the island shape anisotropy observed during growth. We then use our data to measure the anisotropic sticking ratio, yielding a sticking anisotropy ratio of 0.019 ± 0.003. Thus, an end site is roughly 50 times more likely to gain a block than a side site.
Figure 3. 800 × 800 Å STM images showing the growth of islands at 533 K. Time advances from left to right. Coverage increases from 0 to 0.1 ML at a rate of approximately 0.01 monolayers deposited per frame. The movie begins with the clean substrate before deposition. At this temperature 1-D islands form and coalesce. View Java Applet Movie or View Gif AnimationThis result gives us insight into MBE growth of Si on Si(001). It is known that in step flow growth, type-B step edges grow faster than type-A edges, eventually causing double height steps to form. Although most material arriving at a step edge is incorporated at existing kink sites, the creation of new kinks (by addition of material to previously flat sections) is the rate-limiting step for the advance of the edge. Because the side of a 1D island is a type-A edge, adding a block there is like adding a block to a flat section of a type-A step edge. The end of a 1D island is a type-B edge; adding a block there is similar to adding a block to a flat section of type-B step edge. Thus the rapid growth of the type-B step edge and the highly anisotropic island shapes are both results of the sticking anisotropy.
|GaN on Sapphire||2" to 4"||Blue and White LED applications|
|AlN on Silicon Carbide||2" to 4"||Typically used for RF electronic devices such as HEMT|
|AlGaN on Sapphire||2" or 3"||Optoelectronic devices operating in UV spectral region|
|InN on Sapphire||Research grade available in 2"||For work on sensors and high frequency electronic devices|
|InGaN on Sapphire||2" for Green LED||Green LED and green laser Developments|