Material characterization and fabrication of compound semiconductor X-ray detectors

Pasi Kostamo

Research output: ThesisDoctoral ThesisCollection of Articles


In this thesis, dislocations and other crystal defects of compound semiconductor materials were characterized by synchrotron radiation X-ray topography (SR-XRT) and X-ray diffraction (XRD). Crystal defects in GaAs structures grown by hydride vapor phase epitaxy were characterized. GaAs diode components were processed of epitaxial p-i-n structures. The response of the diode components was measured with fluorescent X-ray photons. Results of SR-XRT measurements were compared to the electrical characteristics of GaAs detector diodes. Medipix2 read-out circuit compatible GaAs sensor was processed of epitaxial GaAs wafer. The sensor was bump bonded to the Medipix2 read-out circuit. The response of the manufactured radiation detector was measured with fluorescent photons. GaAs/Ge detector diodes were processed of epitaxial GaAs/Ge structures. Electrical characterization was performed for the GaAs/Ge structures. Crystal defects of GaAs layers grown on high purity germanium substrate were characterized. It was found that the crystal defect density was low in best samples, however, it was observed that arsenic diffusion in germanium substrate dominates the electrical characteristics of the structure and thus the structure can't be used for radiation detector purposes. Crystal defects of TlBr crystals were measured with SR-XRT. Radiation detector components were processed of the TlBr crystals and current-voltage characteristics were measured.The information about crystal defects, which was acquired in this study, can be used to better understand electrical characteristics and performance of various compound semiconductor detector structures.
Translated title of the contributionYhdistepuolijohderöntgendetektorien materiaalitutkimus ja valmistus
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Lipsanen, Harri, Supervising Professor
  • Tuomi, Turkka, Supervising Professor
Print ISBNs978-952-60-7345-3
Electronic ISBNs978-952-60-7344-6
Publication statusPublished - 2017
MoE publication typeG5 Doctoral dissertation (article)


  • GaAs
  • Ge
  • dislocations
  • topography
  • X-ray diffraction
  • X-ray detector

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