Defect characterization of unannealed neutron transmutation doped silicon by means of deep temperature microwave detected photo induced current transient spectroscopy

Unannealed neutron transmutation doped silicon substrates with a target resistivity of approximately $1000Ωcm$ are characterized for radiation induced defects by means of microwave detected photoinduced current transient spectroscopy (MD-PICTS). This technique is a contactless advancement of conventional PICTS and does not require the fabrication of ohmic contacts. Defect spectroscopy by means of MD-PICTS is conducted in a broad temperature range between 30 K and 293 K, which makes it possible to identify energetically shallow as well as deep traps. In addition, a wavelength dependent analysis is performed to determine whether a defect is located at the surface or in the bulk material. Three traps with an average activation energy of $68meV$⁠, $85meV$⁠, and $150meV$ are observed. In addition, an indication for deep defect states with activation energies between $320meV$ and $480meV$ is found. According to the wavelength dependent analysis, it is assumed that all observed traps are bulk defects. Finally, a minority carrier lifetime of approximately 0.7 μs is determined, suggesting that the crystal is heavily damaged by neutron radiation.