Identification and characterization of traps in ingaas short wavelength infrared photodetectors by deep level transient spectroscopy

Avishan, Nardin
Unintentionally added impurities during the epitaxial growth and lattice defects may cause deep level traps in the bandgap of semiconductors. They can strongly affect the electrical and optical properties of semiconductors. Studying these energy levels and providing feedback to the material growth and device fabrication processes are important in order to identify the performance limiting mechanisms and optimize the characteristics of semiconductor devices. Deep Level Transient Spectroscopy (DLTS) technique is commonly used for this purpose. In this thesis, the electrical properties of traps in molecular beam epitaxy (MBE) grown InxGa1-xAs with In mole fractions (x) of 0.53 and 0.83 are identified and characterized. The epilayers were grown on InP substrate. One electron trap at Ec−0.33 eV and one hole trap at Ev+0.15 eV were detected in the lattice-matched In0.53Ga0.47As/InP p-i-n photodiodes with different absorber doping densities. Two hole traps with energy levels of Ev+0.10 eV and Ev+0.31 eV were detected in the lattice-mismatched In0.83Al0.17As/In0.83Ga0.17As/InP heterojunction p-i-n photodetector grown with a linearly graded InxAl1-xAs buffer layer. The results were compared with the trap characteristics reflected by the G-R component of the dark current in the photodetectors fabricated with the epilayer structure and good agreement was obtained. The dominant trap degrading the detector characteristics was found to display extended defect characteristic with a capture cross section of 5.3x10-16 cm2, density of 1.8x1015 cm-3 and activation energy of 0.31 eV.


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Citation Formats
N. Avishan, “Identification and characterization of traps in ingaas short wavelength infrared photodetectors by deep level transient spectroscopy,” M.S. - Master of Science, Middle East Technical University, 2016.