Positron beam-aided characterization and optimization of post-growth defect passivation to enhance IR-detector operability

Infrared detectors based on group III-V materials systems are an emergent technology that promises lower cost and improved manufacturability compared to the most sensitive HgCdTe-based photodiodes. However, tunable wavelength group III-V IR detector materials systems, e.g., InAsSbBi, GaAsBi, etc suffer from non-optimal growth conditions, which results in defects. Defects ranging from Bi segregation, surface droplets, interstitials, and vacancy formation to dangling bonds can generate scattering centers and can be responsible for reduced carrier lifetime and higher dark current. JP Analytical, in collaboration with the University of Texas at Arlington (UTA) proposes to understand the nature of the defects and thereby attain an optimized passivation technique for such defects. Hydrogenation is found to be effective in influencing the electrical properties of Si, group III-V optoelectronic materials, as well as several other heterostructure systems in passivating growth-related defects. While hydrogenation, in general, will be used as a means of passivating defects to enhance the carrier lifetime and to reduce the dark current of the InAsSbBi-based IR detectors, the distinguishing facts of JP Analytical come from the analytical capabilities and hydrogenation innovations. Positron beam-aided defects characterization in a depth-resolved manner will provide defect insight and evidence of passivation. Using a depth-resolved measurement of the Doppler broadening of the electron-positron annihilation radiation, it is possible to obtain selective information regarding charged open volume defects and the chemical environment of the defect site. Sensitivity to the chemical environment of the open volume defect becomes important when the neutral or charged vacancies get passivated by hydrogen.   As such, the intellectual merit offered by JP Analytical and their collaborators at UTA includes the following: (a) Defect characterization: The identification of the electrical effects of and pre and post-passivated materials system can lead to optimized defect passivation, and (b) Hydrogenation at higher temperature and pressure: As the optimized Bi incorporation required higher growth temperature, hydrogenation defect passivation will be evaluated at higher temperatures and under pressure to thermally remove some of the unpassivated or unpinned defect centers without causing Bi to be segregated out of the solid solution.   If successful, positron-beam aided characterization and hydrogenation can be implemented for other materials systems that suffer non-optimal growth conditions to detect and pin down vacancies and passivate defects.