KEYWORDS: Indium nitride, 3D modeling, Indium, Medium wave, Nitrogen, Adsorption, Chemistry, Chemical reactions, Computer simulations, Temperature metrology
A numerical model was developed to simulate vapor deposition in high-pressure chemical vapor-deposition reactors, under different conditions of pressure, temperature, and flow rates. The model solved for steady-state gas-phase and heterogeneous chemical kinetic equations coupled with fluid dynamic equations within a three-dimensional grid simulating the actual reactor. The study was applied to indium nitride (InN) epitaxial growth. The steady-state model showed that at 1050-1290 K average substrate temperatures and 10 atm of total pressure, atomic indium (In) and monomethylindium [In(CH3)] were the main group III gaseous species, and undissociated ammonia (NH3) and amidogen (NH2) the main group V gaseous species. The results from numerical models with an inlet mixture of 0.73:0.04:0.23 mass fraction ratios for nitrogen gas (N2), NH3 and trimethylindium [In(CH3)3], respectively, and an initial flow rate of 0.17 m s-1, were compared with experimental values. Using a simple four-path surface reaction scheme, the numerical models yielded a growth rate of InN film of 0.027 μm per hour when the average substrate temperature was 1050 K and 0.094 μm per hour when the average substrate temperature was 1290 K. The experimental growth rate under similar flow ratios and reactor pressure, with a reactor temperature between 800 and 1150 K yielded an average growth rate of 0.081 μm per hour, comparing very well with the computed values.
The growth of high-quality InN and indium rich group III-nitride alloys are of crucial importance for the development of high-efficient energy conversion systems, THz emitters and detectors structures, as well as for high-speed linear/nonlinear optoelectronic elements. However, the fabrication of such device structures requires the development of growth systems with overlapping processing windows in order to construct high-quality monolithic integrated device structures. While gallium and aluminum rich group III-nitrides are being successfully grown by organometallic chemical vapor deposition (OMCVD), the growth of indium rich group III-nitrides presents a challenge due to the high volatility of atomic nitrogen compared to indium. In order to suppress the thermal decomposition at optimum processing temperatures, a new, unique high-pressure chemical vapor deposition (HPCVD) system has been developed, allowing the growth of InN at temperatures close to those used for gallium/aluminum-nitride alloys.
The properties of InN layers grown in the laminar flow regime with reactor pressures up to 15 bar, are reported. Real-time optical characterization techniques have been applied to analyze gas phase species and are highly sensitive the InN nucleation and steady state growth, allowing the characterization of surface chemistry at a sub-monolayer level. The ex-situ analysis of the InN layers shows that the absorption edge in the InN shifts below 0.7 eV as the ammonia to TMI precursor flow ratio is lowered below 200. The results indicate that the absorption edge shift in InN is closely related to the In:N stoichiometry.
A computer program has been developed to calculate crystal susceptibility tensor components. In addition to previous considerations where molecular polarization tensors have been treated as 1D or 2D, the present program allows the use of the 3D case that appears necessary for non-planar molecules. Calculation of crystal susceptibility is based on the approximation of relatively weak intermolecular forces in relation to intramolecular ones. Local field corrections have been estimated using simple Lorentz form. To provide molecular second-order polarizability, a semiempirical quantum chemical calculation has been carried out using the finite field method incorporated in the MOPAC program.
This investigation explores the effect that aromatic subgroups have on the nonlinear optical properties of highly conjugated multi-dimensional molecules. In particular, carbon-cage fullerenes, porphyrins and phthalocyanines have been studied The optimized geometries were determined from all-electron ab-initio calculations. The nonlinear properties were obtained using the finite field approximation. Data of polarization versus static electric field was obtained from valence-electron semi-empirical calculations using the AMI Hamiltonian. The static electric fields were created using a variety of conditions. Polynomial fits were performed with 14 to 400 data points. The nonlinear properties were extracted from expansions of order four to sixteen. These last three conditions allowed estimation and minimization of the uncertainty in the results. Aromaticity was evaluated by analyzing the molecular geometry.
The Alliance for Nonlinear Optics is a group of seven faculty at five universities who are working together to develop and test nonlinear optical materials. Each school has its own approach to outreach. In general the group has worked with the academic departments to supplement the departmental efforts. Some of the programs are formal, such as the Visiting Scientist Program at New Mexico Highlands University. Others are informal, such as the faculty efforts to interact informally with the high schools in Puerto Rico. One effort that has been successful is Discovery Day or Science Day, a special day when high school students from around the state are invited to the university for programs in science and engineering. This program has become so popular that it will have to be offered twice this year to meet the demand. Students have been very successful in putting on a chemical magic show in area elementary schools.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.