New thermally stimulated emission spectrometer for the detection of ultra-shallow low-density traps

Electron/hole traps alter the optical and electrical properties of materials by creating additional recombination pathways, trapping or providing charge carriers and modifying exciton dynamics. Understanding the defect/trap dynamics is crucial to control the optoelectronic properties of materials, and measuring donor/acceptor ionization energy is critical in semiconductor research. Here, we developed a highly sensitive thermally stimulated emission (TSE) spectrometer for the low temperature regime of 9-325 K to detect and characterize shallow traps in bandgap materials with enhanced sensitivity. It provides a powerful characterization tool for a wide range of semiconductors and electronic and photonic materials. This technique is ideal where electrical methods cannot be used for donor/acceptor characterization as in powder, irregular shape and thickness, and high resistive samples. The performance of the spectrometer was tested on Ce doped Y3Al5O12 single crystals, and the measurements identified several shallow levels that cannot be detected with conventional methods. Then, its capabilities were further demonstrated by detecting a shallow level in Ga2O3, which is emerging as an exceptional semiconductor for high-power devices and optoelectronics. A sophisticated data analysis technique based on the three-point analysis (TPA) approach was applied to deconvolute the highly overlapped TSE signals. The developed ultra-low temperature spectrometer together with the TPA deconvolution method provides a unique tool for studying exciton dynamics in photonic materials and measuring donor/acceptor ionization energies and densities in luminescent semiconductors. It will advance material characterization and development for a wide range of applications including lasers, electronic and illumination devices, and detectors for medical diagnostic and nuclear applications.