| AVS 58th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing Division | Thursday Sessions |
| Session EM-ThP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | Nikolaus Dietz, Georgia State University |
| Authors: | M.K.I. Senevirathna, Georgia State University S. Gamage, Georgia State University R. Atalay, Georgia State University J. Hong, Georgia Institute of Technology N. Dietz, Georgia State University A.G.U. Perera, Georgia State University |
| Correspondent: | Click to Email |
Indium nitride (InN) and indium-rich group III-nitride alloys may have great potential for high efficient energy conversion devices such as solar cells, high speed optoelectronic devices, and various types of light emitting device structures. Scientists are exploring several different growth methods and various characterization methods to improve the material quality and to understand the optical, structural, and electronic properties of these epilayers. However, till today, the growth of high quality InN alloys and epilayers is still a challenge, mainly due to low InN dissociation temperature and due to stoichiometry instabilities at optimum growth conditions. InN epilayers exhibit significant different physical properties depending on the growth techniques (PAMBE, MBE, MOCVD, etc.) and the substrate material used. At present, low-pressure CVD based growth methods are limited to InN growth temperatures at or below 600°C, which creates problems related to a suited nitrogen precursor, since the ammonia decomposition at these growth temperatures is insufficient. To stabilize InN at higher growth temperature, we explored the growth of InN by high-pressure chemical vapor deposition (HPCVD) at 10 bar and 15 bar reactor pressures. Under these growth conditions the growth temperature can be increased to around 800 °C, resulting in improved ammonia decomposition and smaller group III/N precursor ratio.
This contribution presents results on the effect of the layer thickness on the physical properties of epitaxial InN layers. All InN layers where grown on GaN/sapphire (0001) templates under identical growth conditions, only the growth time was varied. Fourier transform IR reflectance (FTIR) spectroscopy was used to analyze the film thickness and the optoelectronic layer properties. We will present results on the free carrier concentration and mobility as a function of layer thickness. The reflectance spectra were simulated using a Lorentz-Drude model and a multilayer stack model, which allows determining the phonon frequencies, dielectric function, plasma frequency, and damping parameters. From these, the free carrier concentration and mobility for each layer can be calculated. The crystalline quality of the epilayers has been characterized by XRD 2theta- omega scans and by Raman spectroscopy analysis.