A study of the characteristics of intrinsic GE and CdTe prepared by laser-induced diffusion

number: 
2714
إنجليزية
Degree: 
Author: 
Layth Mokhles Abduljabbar
Supervisor: 
Dr. Ziad T. Al-Dahan
year: 
2012
Abstract:

Germanium and Cadmium Telluride detectors were fabricated by doping n-type germanium samples with indium and boron while n-type cadmium telluride sample doped with indium in water environment. For germanium samples the doping was achieved by coating the germanium wafers with indium using thermal evaporation process then Nd:YAG laser of wavelength 1064 nm is used to diffused the indium inside the germanium with different energy densities of (1.6 and 4) J/cm2 .Because of the boron has a high boiling point, then thermal evaporation process can not be used and boron powder was spread over germanium and then diffused using different energy densities of (1.6 and 4) J/cm2. While for cadmium telluride sample the doping was achieved by coating the cadmium telluride with indium and then Nd:YAG laser (SHG) with wavelength 532 nm is used to diffused the indium inside the cadmium telluride with energy density of 4 J/cm2 in water environment. From XRD measurements the grain size for Ge samples that are doped with boron was increased from (26.38 to 30.12)Ǻ as the energy density increased from (1.6 to 4) J/cm2, while for Ge samples that are doped with indium was increased from (2.63 to 2.77) Ǻ when the energy density increased from (1.6 to 4) J/cm2. The grain size has a value of (5.94) Ǻ for CdTe sample that is doped with indium. FTIR measurements were used to measure the behavior of the absorption and transmission for Ge and CdTe samples. From this measurements the absorption coefficient can be calculated and its average values were increased from (34.6 to 56.37 )cm-1 and from (26.96 to 39.8)cm-1 for the Ge samples that are doped with indium and boron respectivity when the energy density increased from (1.6 to 4) J/cm2.While for CdTe sample the average value of the absorption coefficient is (19.43)cm-1. Seeback coefficient was calculated from thermoelectric measurements and has a value (0.133) mV/K for Ge sample and (0.25) mV/K for CdTe sample. General characteristics of a photodetectors such as responsivity, quantum efficiency and detectivity were measured and all fabricated detectors show a good responce for CO2 laser.