Surfactant controlled growth of GaInP by organometallic vapor phase epitaxy

Journal ArticleThe effect of the surfactant Sb has been studied for GaInP semiconductor alloys grown by organometallic vapor phase epitaxy. Dramatic changes in the optical and electrical properties of GaInP with CuPt ordering have been observed. A small concentration of triethylantimony TESb in the vapor is found to cause Sb to accumulate at the surface. In situ surface photoabsorption analysis indicates that Sb changes the surface bonding by replacing the 1 10 P dimers that are responsible for the formation of the CuPt structure during growth with 1 10 Sb dimers. As a result, the degree of order for the GaInP layers is decreased, as shown by transmission electron diffraction studies. The 20 K photoluminescence spectra show a 131 meV peak energy increase for GaInP layers grown on vicinal substrates when a small amount of Sb Sb/P(v) 4 10 4 is added to the system during growth. The use of surfactants to control specific properties of materials is expected to be a powerful tool for producing complex structures. In this article, the growth of heterostructures by modulating the Sb concentration in the vapor is demonstrated

Step structure and ordering in Zn-doped GaInP

Journal ArticlePresents the results of a study of Zinc dopant effects on both step structure and ordering in GaInP in an effort to further clarify the disordering mechanism. Comparison of the results obtained for Zinc with those reported for tellurium; Experiment; Results; Discussion; Conclusion

Step structure and ordering in Te-doped GaInP

Journal ArticleThe step structure and CuPt ordering in GaInP layers grown by organometallic vapor phase epitaxy on singular GaAs substrates have been investigated as a function of Te (DETe) doping using atomic force microscopy, and electrical and optical properties measurements. The degree of order decreases for Te concentrations of 1018 cm3. It is estimated from the photoluminescence peak energy to be approximately 0.5 for undoped layers and the layers are completely disordered at sufficiently high Te doping levels. The bandgap energy is changed by 110 meV as the Te doping level increases from 1017 to 1018 cm3. The step structure also changes markedly over the range of doping that produces disordering, from a mixture of monolayer and bilayer steps for undoped layers to solely monolayer steps for electron concentrations exceeding 1018 cm_3. For growth at 670 °C, the spacing between 1 10 steps increased by over an order of magnitude as the doping level was changed over the range investigated, while the step spacing between 110 steps increased only slightly. In general, Te doping significantly improves the surface morphology viewed using atomic force microscopy. The degree of order and surface structure are changed at exactly the same doping concentration. This suggests that the disordering may be controlled by the fast propagation of 1 10 steps due to kinetic effects at the step edges. A qualitative model is presented to explain these effects

Step structure and ordering in GaInP

Journal ArticlePresents information from an experiment on the step structure and ordering in GalnP. Information on the step spacing and degree of order in the epitaxial layers; Details on the experiment; Results from the experiment

Te doping of GaInP: ordering and step structure

Journal ArticleThe donor Te has been added to GaInP during organometallic vapor phase epitaxial growth using the precursor diethyltelluride. In agreement with previous studies, the addition of high Te concentrations leads to the elimination of the CuPt ordering observed in undoped layers. The degree of order is estimated from the low temperature photoluminescence peak energy to decrease from 0.5 at Te concentrations of 2 1017 cm 3 to 0 for Te concentrations of 6 1017 cm 3. This is verified by transmission electron diffraction studies, which show the elimination of the ½ 111 superlattice spots at high Te doping levels. A remarkable change in the surface structure is found to accompany this decrease in ordering: The surfaces become much smoother. Step bunching is observed to disappear for the vicinal GaAs substrates, misoriented from 001 by 3° in the B direction, and three-dimensional island or mound formation is eliminated for the singular 001 substrates. A qualitative model is presented explaining this behavior based on the effect of Te on the step structure and the bonding at step edges, both of which affect the adatom sticking at steps

Influence of tellurium doping on step bunching of GaAs (001) vicinal surfaces grown by organometallic vapor phase epitaxy

Journal ArticleAtomic force microscopy has been used to investigate the influence of controlled tellurium Te incorporation on the step structure of GaAs grown by organometallic vapor phase epitaxy on vicinal 001 surfaces. Te doping, using the precursor diethyltelluride, is found to markedly decrease the surface roughness. Step bunching, observed for undoped layers, is totally eliminated. Only monolayer steps are formed for Te concentrations of 4 1017 cm 3. A model is proposed to account for these effects and the results reported previously for GaInP

Adsorption and desorption of the surfactant Sb on GaInP grown by organometallic vapor phase epitaxy

Journal ArticleIt has been determined that ordering has a profound effect on the bandgap energy of many compound semiconductor alloys. Therefore, ordering must be controlled for devices such as solar cells, light emitting diodes and diode lasers. Since ordering depends on the surface properties during organometallic vapor phase epitaxy (OMVPE), the ability to control the surface has been shown to be important for controlling ordering and for producing heterostructures and quantum wells. However, perhaps equally as important as the affect of ordering on the bandgap is the fundamental information that it can provide about the surface during growth. This paper reports on the use of time dependent surface photoabsorption (SPA) measurements to determine the rate of change in the P dimer concentration when TESb is added to and removed from the reactor. In particular, the time constants for the transients are presented and compared with the Langmuir model for adsorption and desorption of the surfactant. Transients in the Sb surface concentration were also indirectly determined from secondary-ion mass spectroscopy (SIMS) measurements on a GaInP heterostructure where TESb was added during growth of one of the layers

Thermopower of gapped bilayer graphene

We calculate thermopower of clean and impure bilayer graphene systems. Opening a band gap through the application of an external electric field is shown to greatly enhance the thermopower of bilayer graphene, which is more than four times that of the monolayer graphene and gapless bilayer graphene at room temperature. The effect of scattering by dilute charged impurities is discussed in terms of the self-consistent Born approximation. Temperature dependence of the thermopower is also analyzed.Comment: 8 pages, 5 figures; An inconsistency in the definitions of Eq.(17) and (18) in version 1 is found and correcte