| 1. |
- Baskar, K., et al.
(författare)
-
Surface morphology and localised states of GaInNAs single quantum wells grown by MOVPE
- 2003
-
Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 248, s. 431-436
-
Tidskriftsartikel (refereegranskat)abstract
- GaInNAs/GaAs single quantum wells (QWs) have been grown by metalorganic vapour phase epitaxy (MOVPE). The surface morphology has been studied by atomic force microscopy (AFM). The density of pits observed on the surface of QW structures was found to depend on the growth temperature and dimethylhydrazine (DMHy) flow. Cross-sectional AFM image showed the presence of defects at the interface of GaInNAs/GaAs. The low temperature photoluminescence characteristics of the QWs as a function of growth temperature. DMHy flow and density of surface pits have been discussed. The origin of pit formation is addressed based on the pyrolysis products present during the growth of QWs. The results suggest that higher growth temperature maybe desirable to obtain good quality GaInNAs QWS.
|
|
| 2. |
- Bertone, Daniele, et al.
(författare)
-
Etching of InP-based MQW laser structure in a MOCVD reactor by chlorinated compounds
- 1998
-
Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 195:1-4, s. 624-629
-
Tidskriftsartikel (refereegranskat)abstract
- Four different chlorinated compounds: 2-chloropropane, dichloromethane, chloroform and carbon tetrachloride have been used to etch InGaAsP/InP MQW laser structures partially masked. Etching experiments were performed in a home-made LP-MOCVD reactor with argon or argon + hydrogen as carrier gas, using phosphine (PH3) or tertiarybutylphosphine (TBP) to prevent thermal decomposition. The etching temperature as well as the chlorinated compound flow were varied to obtain the best trade-off between etch rate and surface morphology. The optimized experimental conditions were applied to etch mesa stripes in a SCH-MQW laser structure, for the first time to our knowledge, followed by lateral InP : Fe regrowth in the same step. Threshold current as low as 4 mA (best value)-6 mA (typical value) and differential quantum efficiency higher than 20% for SI-BM MQW laser have been achieved.
|
|
| 3. |
- Buyanova, Irina, 1960-, et al.
(författare)
-
Intrinsic modulation doping in InP-based structures : properties relevant to device applications
- 1999
-
Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 201-202, s. 786-789
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we study device-relevant issues, such as doping efficiency and thermal stability, of recently proposed intrinsic modulation doping approach where intrinsic defects (PIn antisites) are used as a carrier source instead of impurity dopants. The InP/InGaAs heterostructure designed to resemble high electron mobility transistor (HEMT) structures, where all the layers were grown at a normal growth temperature 480°C except for the top InP layer which was grown at 265°C, was used as a prototype device. A comparison between the intrinsically doped structure with extrinsically doped HEMTs, which have an identical design except that the top InP layer was instead Si-doped and was grown at 480°C, reveals a high efficiency of the intrinsic doping. The thermal stability of the intrinsically doped HEMT is examined by annealing at temperatures 400-500°C relevant to possible processing steps needed in device fabrication. The observed severe reduction of the carrier concentration after annealing performed without phosphorous gas protection is attributed to the known instability of an InP surface at T>400°C. Thermal stability of the intrinsically doped HEMT is shown to be improved by using an InP cap layer grown at 480°C.
|
|
| 4. |
|
|
| 5. |
- Cerreta, M.K., et al.
(författare)
-
Contact nuclei formation in aqueous dextrose solutions
- 1990
-
Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 102:4, s. 869-876
-
Tidskriftsartikel (refereegranskat)abstract
- A laser Raman microprobe was used in situ to observe the growth of alpha dextrose monohydrate on alpha anhydrous dextrose crystals. The Raman spectra indicate growth of the monohydrate below 28.1°C, but the presence of only the anhydrous form above 40.5°C. Contact nucleation experiments with parent anhydrous crystals yielded only monohydrate nuclei below 28.1°C, while contacts in solutions between 34.5 and 41.0°C produced both crystalline forms, and contacts in solutions above 43.5°C produced only anhydrous nuclei. The inability of the monohydrate to grow on anhydrous crystals in the same solution that forms the two crystalline phases with a single contact precludes a simple attrition mechanism of nuclei formation. For the same reason, the hypothetical mechanism involving parent crystal stabilization of pre-crystalline clusters, allowing the clusters to grow into nuclei, is also contradicted. A third, mechanism, which may be a combination of the two, is believed to apply.
|
|
| 6. |
- Cerreta, M.K., et al.
(författare)
-
The structure of aqueous solutions of some dihydrogen orthophosphates by laser Raman spectroscopy
- 1987
-
Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 84:4, s. 577-588
-
Tidskriftsartikel (refereegranskat)abstract
- Powdered crystals and pure, aqueous solutions of ammonium, sodium, and potassium dihydrogen orthophosphates in concentrations ranging from 0.01M to supersaturated were investigated at 30°C using laser Raman spectroscopy between 700 and 1350 cm-1. With increasing solute concentration, the peak position of the 875 cm-1 P-(OH)2 symmetric strech band increased. Extreme asymmetry in the 1075 cm-1 P=O2 symmetric stretch band developed to lower energy. The integrated intensity ratio of the 875 cm-1 band to the 1075 cm-1 band envelope remained constant. These observations are consistent with anion-anion association via hydrogen bonds. Deconvolution of the spectral bands showed only 40% and 20% of the phosphates exist as monomers in saturated potassium and ammonium solutions, respectively, and that anion association does not cease at the dimer. The spectra provided no evidence of quasi-crystalline entities in solution. The necessary breaking and reforming of hydrogen bonds during the growth process can explain rapid z-direction growth, growth activation energy, and the rate-limiting surface growth mechanism.
|
|
| 7. |
- Chakraborty, Reena, et al.
(författare)
-
Steady state fluorescence spectroscopy of pyranine as a trace extrinsic probe to study structure in aqueous sugar solutions
- 1992
-
Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 125:1-2, s. 81-96
-
Tidskriftsartikel (refereegranskat)abstract
- The steady state fluorescence behavior of pyranine has been monitored in aqueous solutions of sucrose, glucose, fructose, and lactose. In each case it is possible to use the ratio of peak intensities at 440 and 511 nm (the PIR) as an indicator of the degree of supersaturation of the sugar solutions. We observed both bulk water and water of solvation in all solutions examined, regardless of degree of sapersaturation. In each case the amounts of bulk water and water of solvation per molecule of sugar appear to be nearly equal at saturation. We did not observe any evidence of solvent exclusive clusters in any of the systems we studied
|
|
| 8. |
- Danielsson, Örjan, 1973-, et al.
(författare)
-
Growth rate predictions of chemical vapor deposited silicon carbide epitaxial layers
- 2002
-
Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 243:1, s. 170-184
-
Tidskriftsartikel (refereegranskat)abstract
- Complete 3D simulations of a silicon carbide chemical vapor deposition (CVD) reactor, including inductive heating and fluid dynamics as well as gas phase and surface chemistry, have been performed. For the validation of simulated results, growth was conducted in a horizontal hot-wall CVD reactor operating at 1600°C, using SiH4 and C3H8 as precursor gases. Simulations were performed for an experimental hot-wall CVD reactor, but the results are applicable to any reactor configuration since no adjustable parameters were used to fit experimental data. The simulated results obtained are in very good agreement with experimental values. It is shown that including etching and parasitic growth on all reactor walls exposed to the gas greatly improves the accuracy of the simulations. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 9. |
- Danielsson, Örjan, et al.
(författare)
-
Investigation of the temperature profile in a hot-wall SiC chemical vapour deposition reactor
- 2002
-
Ingår i: Journal of Crystal Growth. - : ScienceDirect. - 0022-0248 .- 1873-5002. ; 235:1-4, s. 352-364
-
Tidskriftsartikel (refereegranskat)abstract
- The chemical vapor deposition (CVD) technique is widely used to grow epitaxial layers of silicon carbide. To meet the demands for high quality epitaxial layers, which have good morphology and a minimum variation of the doping and thickness, a good knowledge of the CVD process is essential. The present work uses a simulation tool to investigate several parameters influencing the heating of a hot-wall CVD reactor. The simulations are set up as 2D axisymmetric problems and validation is made in a 2D horizontal hot-wall CVD reactor. By applying the knowledge achieved from the simulations, the temperature profile is optimized to give as large area as possible with homogeneous temperature. New susceptor and coil designs are tested. A very good agreement between the simulated and the measured results is obtained. The new design has a temperature variation of less than 0.5% over more than 70% of the total susceptor length at an operating temperature of 1650°C. In addition, the power input needed to reach the operating temperature is decreased by 15% compared to the original design. 3D simulations are performed to show that the changes made in the 2D case give similar results for the real 3D case.
|
|
| 10. |
- Danielsson, Örjan, et al.
(författare)
-
Predicted nitrogen doping concentrations in silicon carbide epitaxial layers grown by hot-wall chemical vapor deposition
- 2003
-
Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 250:3-4, s. 471-478
-
Tidskriftsartikel (refereegranskat)abstract
- A simple quantitative model for the surface adsorption of nitrogen has been developed to simulate the doping incorporation in intentionally doped 4H-SiC samples during epitaxial growth. Different reaction schemes are necessary for the two faces of SiC. The differences are discussed, and implications to the necessary model adjustments are stressed. The simulations are validated by experimental values for a large number of different process parameters with good agreement.
|
|
