Date of Graduation
2007
Document Type
Thesis
Abstract
As a nonlinear optical material, CdGeAs2 can be used in frequency conversion applications in the infrared. This work is going to explain the details of optical properties by using Hall effect measurements. The temperature dependent Hall effect measurements were conducted on about 100 CdGeAs 2 bulk samples which were grown by the horizontal gradient freeze technique. The Hall data were fitted to extract the electrical parameters acceptor concentration, donor concentration, activation energy and mobility ratio. Correlations between Hall data and both absorption and photoluminescence data were determined. These data consistently support the defect model that has one shallow donor, one shallow acceptor, and one deep acceptor in this material. For as-grown p-type samples with hole concentrations of about 10 15-1016 cm-3 at room temperature, the observed 5.5 μm absorption band in those samples increases with increasing concentration of the shallow acceptor. The carrier transport equation is well fitted to the Hall measurement carrier concentration. The absorption coefficient at 5.5 μm is correlated with the hole concentration p of p-type CdGeAs2 samples. The activation energy for dilute carrier concentration Ea0 was extrapolated. From measured Hall mobility data, the non-polar optical phonon scattering process and ionized impurity scattering are suggested as the dominant processes in the high temperature and low temperature ranges, respectively, in the p-type CdGeAs2 samples. For n-type samples doped with In, Se, and Te, the electron concentrations exceed 1017 cm-3. Free carrier absorption is observed and the large concentration of electrons causes a change in electron effective mass due to the non-parabolicity of the conduction band. The non-parabolic conduction band was accounted for and the non-parabolicity coefficient α np expression was obtained for CdGeAs2. The non-parabolic conduction band effects were used to account for shifts in photoluminescence peak energies. For p-type samples doped with Fe, Al, Ga, and Cu, the hole concentrations vary from 1015 cm-3 to 1018 cm -3 at room temperature and the both shallow and deep acceptors are present. The potential fluctuation Γ model is used to predict shifts in energy of the near-band-edge photoluminescence transition.
Recommended Citation
Xu, Chunchuan, "Correlation of electrical and optical properties of cadmium germanium arsenide." (2007). Graduate Theses, Dissertations, and Problem Reports. 10057.
https://researchrepository.wvu.edu/etd/10057