Dependence of activation energy of mass transport limited region on the photospectrum of photons participating in rapid photothermal assisted chemical vapor deposition

In this letter, we demonstrate the importance of high energy photons (λ<800nm) in reducing the activation energy and providing higher growth rates and low defect densities for the materials deposited by rapid photothermal processing assisted chemical vapor deposition (CVD). The dependence of growth rate, structural properties, and electrical properties of Y₂O₃/Si structure on the photospectrum reaching at the Y₂O₃/Si interface has been studied. The observation that high energy photons result in the reduction of activation energy of mass transport limited region has direct advantage of depositing various electronic materials by CVD at low processing temperatures.     

A comparative study of defect states in evaporated and selenized CIGS(S) solar cells

Current‐voltage, admittance spectroscopy, and drive‐level capacitance profiling measurements were taken on Cu(In_1−xGa_x)(Se_1−yS_y)₂ solar cell devices. The devices were made using two different types of absorbers. One set of absorbers was deposited via physical vapor deposition, while the other set of absorbers was made by selenization of metal precursors. Additionally, each type of absorber was completed with one of two different types of buffer treatments: a CdS layer or a cadmium partial electrolyte surface modification. The devices with the evaporated absorbers had larger values of V_OC, higher carrier densities, lower densities of trapping defects, and likely shallower gap states. Results were qualitatively similar for the CdS and partial electrolyte buffers. Copyright © 2005 John Wiley & Sons, Ltd.     

Optical and microstructural characterization of the effects of rapid thermal annealing of CdTe thin films grown on Si (100) substrates

The effects of rapid thermal annealing (RTA) on CdTe/Si (100) heterostructures have been studied in order to improve the structural quality of CdTe epilayers. Samples of CdTe (111) polycrystalline thin films grown by vapor phase epitaxy (VPE) on Si (100) substrates have been investigated. The strained structures were rapidly thermally annealed at 400°C, 450°C, 500°C, 550°C, and 600°C for 10 sec. The microstructural properties of the CdTe films were characterized by carrying out scanning electron microscopy (SEM), x-ray diffraction (XRD), and atomic force microscopy (AFM). We have shown that the structural quality of the CdTe epilayers improves significantly with increasing annealing temperature. The optimum annealing temperature resulting in the highest film quality has been found to be 500°C. Additionally, we have shown that the surface nucleation characterized by the island size distribution can be correlated with the crystalline quality of the film.     

Preparation of PbTiO3 thin films by plasma enhanced MOCVD and the effect of rapid thermal annealing

Dielectric PbTiO₃-thin films were prepared on p-Si(100) substrate by plasma enhanced metalorganic chemical vapor deposition using high purity Ti(O-i-C₃H₇)₄, Pb(tmhd)₂, and oxygen. As-deposited films were post-treated by rapid thermal annealing method, and the effect of annealing was examined under various conditions. The deposition process was controlled by mixed-control scheme at temperatures lower than 350°C, but controlled by heterogeneous surface reaction at temperatures greater than 350°C. The as-deposited films showed PbO structure at 350∼400°C, but (100) and (101) PbTiO₃ orientations started to appear at 450°C. The deposition rate was increased with rf power due to the enhanced dissociation of Ti and Pb precursors. It was found that the concentration of oxygen plays an important role in crystallization of PbTiO₃ during the rapid thermal annealing. A linear relationship was obtained between the dielectric constant of PbTiO₃ films and the annealing temperature. However, the surface roughness and leakage current density increased mainly due to the defects caused by volatilization of lead and the interface layer formed during the high temperature annealing.     

A study of self-aligned formation of C54 Ti(Si1−xGex)2 to P+ and N+ Si0.7Ge0.3 alloys using rapid thermal annealing

In this paper, solid state reactions of titanium with boron and phosphorus doped Si_0.7Ge_0.3 alloys have been investigated for application in a self-aligned germanosilicide process. Wet chemical etching of the germanosilicide with respect to unreacted Ti in a solution of 1:1:5 NH₄OH:H₂O₂:H₂O has been investigated. Characterization was performed using four-point probe sheet resistance measurements, x-ray diffraction, cross-sectional transmission electron microscopy, Nomarski optical imaging, and scanning electron microscopy. The C54 Ti(Si_1−yGe_y)₂ phase was observed to form for reactions on both boron and phosphorus doped Si_0.7Ge_0.3 alloys. Grain structures of the C54 phases were found to be similar to grain structures of intrinsic alloy reactions with lateral grain dimensions on the order of 0.3 Μm. Resistivities of 22 ΜΩ-cm have been determined for the boron and phosphorus reactions. Although the germanosilicide phases were observed to etch slowly in 1:1:5 NH₄OH:H₂O₂:H₂O, which is conventionally used in the self-aligned titanium silicide process, the much higher etch rate of titanium nitride compounds and unreacted Ti provided for a self-aligned germanosilicide process. A first anneal in a nitrogen ambient was found to be necessary to eliminate lateral silicidation over surrounding oxide during self-aligned germanosilicide formation.