The Effect of Postgrowth Annealing on the Dislocation Structure of Germanium Crystals

The effect of post-growth annealing (PGA) on dot-in-well (DWELL) structures grown on Si substrates has been studied. The photoluminescence (PL) measurements showed that, compared to the DWELL structures directly grown on GaAs, the PGA process induces a distinct difference in the tuning of the emission properties. Then, transmission electron microscopy imaging of the samples revealed that PGA improved the uniformity of quantum dots (QDs) while the size of the QDs increased, in agreement with a corresponding red shift and a decrease of the full width at half maximum in the PL emission spectrum. Finally, energy-dispersive x-ray linescan provided a quantitative analysis of the composition change of DWELL grown on Si in the as-grown, 700 °C annealed, and 800 °C annealed samples. The change in the InL/GaK concentration ratio became gradual between the QDs and surrounding materials after 800 °C annealing. The analysis of the optical properties, morphology evolution, and compositional change of the QDs as a function of the annealing temperature showed good agreement.

We have investigated the effect of post-growth thermal annealing on the defect surface of patterned GaAs on silicon. Significant improvements in defect structure of the patterned GaAs were observed by transmission electron microscopy (TEM) after short anneal times (15 min) at temperatures as low as 750 °C. At anneal temperatures of 950 °C, long-range single-crystal lateral regrowth of the original polycrystalline GaAs deposited over the amorphous patterning mask was observed. Micro-Raman spectroscopic characterization of the GaAs grown on the oxide/nitride mask corroborated the TEM results by showing a significant improvement in the crystalline quality of patterned GaAs on silicon following post-growth annealing.

Effects of post-growth annealing on the optical properties of self-assembled GaAs/AlGaAs quantum dots

The influence of the Fe∕Ga0.9Al0.1As interface on spin injection into a spin light-emitting diode is studied. Spin injection is found to depend strongly on the interfacial doping profile demonstrating the importance of band bending in the semiconductor near the interface. The effect of post-growth annealing on spin injection from Fe contacts into GaAs-based spin light-emitting diodes is also examined. Post-growth annealing up to 250 °C is found to increase the spin injection efficiency. It is demonstrated that the annealing modifies electronic properties of the Fe∕Ga0.9Al0.1As interface, as evidenced by an increase of the Schottky barrier height.

In the present work, ZnO/CuO composite nanostructures have been grown on fluorine doped tin oxide coated glass substrate by aqueous chemical growth method. To observe the effect of post growth annealing (500 degrees C, 1 min) on the structural properties of ZnO nanorods scanning electron microscope and X-ray diffraction techniques have been utilized. SEM images of post growth annealed (post growth annealed) sample reveal that the average diameter of ZnO NRs has considerably increased in comparison with as grown sample. Moreover after post growth annealing the ZnO NRs showed more clearly hexagonal wurtzite structure. Beside this the NRs are also uniform and well aligned with a high aspect ratio of similar to 10. In XRD pattern the strongly intense (002) peak of the post growth annealing sample suggest that the crystal quality of the NRs have also been improved significantly. Since the structural improvement have a significant impact on charge transport properties as well, therefore the effect of post growth annealed has also been investigated by the electrical characterization of ZnO/CuO based heterojunction. The current-voltage measurements of the post growth annealed sample showed improvement in the current in comparison with as grown sample. The impedance study has also confirmed that the post growth annealed has influence on the electrical properties. The presented post growth annealed heterojunction of ZnO/CuO may have space in applications like sensors and oxide based diodes in the devices fabrication.

The effect of post-growth annealing and magnetic field on the two-way shape memory effect (TWSME) of Ni52Mn24Ga24 single crystals was investigated. We found that samples subjected to a two-step post-growth annealing can provide a better TWSME than that of directly quenching from the parent phase. By way of comparison, the martensitic microstructures of samples, subjected to two different post-annealing treatments, were studied by means of optical and electron microscopy. Moreover, we found that the magnitude and direction of TWSME can be changed optionally by selecting the strength and direction of the magnetic field. The work output by the sample on a fixed magnetic field of 1.2 T was calculated to be 12 kJ m-3, which is comparable to that of Terfenol-D actuators, being of order 10 kJ m-3 reported by Clark et al (1988 J. Appl. Phys. 63 3910).

Effect of the post-growth annealing on the morphology of a Ge mesa selectively grown on Si was studied from the viewpoint of near-infrared photodiode applications. By ultrahigh-vacuum chemical vapor deposition, Ge mesas were selectively grown at 600°C on Si (001) substrates partially covered with SiO2 masks. The as-grown Ge mesas showed trapezoidal cross-sections having a top (001) surface and {311} sidewall facets, as similar to previous reports. However, after the subsequent post-growth annealing at -800°C in the ultrahigh-vacuum chamber, the mesas were deformed into rounded shapes having a depression at the center and mounds near the edges. Such a deformation cannot be observed for the samples annealed once after cooled and exposed to the air. The residual hydrogen atoms on the Ge surface from the germane (GeH4) decomposition is regarded as a trigger to the observed morphological instability, while the final mesa shape is determined in order to minimize a sum of the surface and/or strain energies.

Effect of thermal oxidation on the optical, electrical, and chemical properties of zinc nitride films grown by reactive magnetron sputtering

Preferential orientation, microstructure and functional properties of SnO2:Sb thin film: The effects of post-growth annealing

CoFeB/MgO/CoFeB tri-layer thin-film stacks have been widely used in the design of STT-RAM devices as functional magnetic-tunnel-junction (MTJ) structures. The materials properties of the CoFeB and MgO layers, including composition and lattice quality, have been extensively researched from the stand point of optimizing for the best MTJ performance. On the other hand, post-growth annealing is required for the MTJ structure to acquire its functional property, i.e. its TMR performance. In this work, we have studied the various possible effects resulting from the post-growth annealing process. Specifically, we show that the post-growth annealing causes boron in the top and bottom CoFeB layers to migrate into the adjacent Ta layers as well as deterioration in lattice quality of the MgO layer. Furthermore, we evaluate other effects that could be possibly induced during the annealing process, including Ta diffusion and layer intermixing in the CoFeB/MgO/CoFeB tri-layer structure. The post-growth annealing causes little change in the Ta diffusion and the layer intermixing. These annealing effects were also evaluated with respect to variations in the MgO growth process; more specifically, an additional natural oxidation treatment during the MgO layer deposition and the insertion of a Fe layer before the MgO layer. Our results indicate that the addition of a natural oxidation process during the MgO deposition process and the insertion of a thin-layer of Fe before the MgO layer both lead to a reduction in the layer intermixing between the MgO and the CoFeB layer and to an improvement in MgO lattice quality. We also show that the post-growth annealing does not alter the beneficial effect of these MgO growth process modifications.

The effect of post-growth annealing at 500, 600, and 700 °C on the electrical characteristics of C-doped p+-GaAs/n-AlGaAs junction diodes fabricated with metalorganic chemical vapor deposition layers has been investigated. Recombination current is reduced by post-growth annealing at 600 and 700 °C, but not at 500 °C. The current reduction is primarily attributed to the dramatic reduction of 0.55 eV deep levels, which may be oxygen related complex levels. Under present annealing conditions, no degradation of carrier profiles near the p+-n junction is detected. Thus, post-growth annealing at temperatures of 600 °C or higher is a promising method for reducing recombination centers in the C-doped p+-GaAs/n-AlGaAs junction.

Effects of postgrowth rapid thermal annealing (RTA) on structural and electrical properties of an In0.52Al0.48As∕In0.52Ga0.48As metamorphic high-electron-mobility transistor (MHEMT) structure grown on a GaAs substrate utilizing a compositionally graded InAlAs∕InGaAlAs buffer layer were investigated. High-resolution triple-axis x-ray diffraction, photoluminescence, and van der Pauw–Hall measurements were used for the investigation. While the RTA improved the structural property of the MHEMT, it degraded the channel mobility of the MHEMT due to defect-assisted impurity redistribution.

Effect of post-growth rapid thermal annealing on bilayer InAs/GaAs quantum dot heterostructure grown with very thin spacer thickness

Photoluminescence spectroscopy of Ga(In)NAs quantum wells for emission at 1.5 μm

Effects of post-growth annealing on the performance of CdZnTe: In radiation detectors with different thickness