Defect and Passivation Engineering for Reducing Background Carrier Concentration Correlating Improved Minority Carrier Lifetime and Mobility of GeSn/SiGeSn Materials System

(Si)GeSn-based all-group IV semiconductors have gained significant attention due to their potential for achieving monolithic integration of electronics and photonics on a single platform. The incorporation of Sn allows the bandgap to be tuned across short- to long-wavelength IR region without introducing significant strain. Increasing Sn content narrows the bandgap, however, leads to a higher intrinsic carrier concentration. This higher carrier concentration can enhance Auger recombination, a non-radiative process involving three carriers, which becomes more significant as the bandgap decreases, thereby limiting the minority carrier lifetime. (Si)GeSn alloys suffer from non-optimal growth constrains leading to the formation of defects. While point defects are known to impact carrier mobility and introduce recombination centers, there is also speculation that the intrinsic carrier concentration associated with these defects may contribute to the Auger-limited minority carrier lifetime. JP Analytical, in collaboration with North Carolina State University, proposes to understand the nature of point defects and vacancies, characterize their impact on intrinsic carrier concentration and mobility, and develop an optimized passivation technique. JP Analytical has recently demonstrated an increase in carrier lifetime in hydrogenated InAsSbBi-based IR detector materials, which also suffer from non-optimal growth constraints. Through a non-optimized process, JP Analytical has also demonstrated the potential of hydrogenation in GeSn/SiGeSn single quantum wells, increasing carrier lifetime and photoluminescence intensity, likely due to the electrical passivation of deep acceptor states. While hydrogenation will be used to passivate point defects, reduce carrier concentration, enhance carrier lifetime, and reduce the dark current of GeSn/SiGeSn-based IR detectors, JP Analytical's distinguishing factors lie in its analytical capabilities and hydrogenation innovations. Specifically, hydrogenation at lower temperatures and higher pressures will be evaluated. Since optimized Sn incorporation requires lower growth temperatures, defect passivation will be conducted at room temperature and under high ambient pressure to remove unpassivated or unpinned defect centers without causing Sn segregation from the solid solution. Due to the sensitivity of open volume defects to the chemical environment, positron beam-aided defect characterization will provide insights and evidence of passivation when neutral or charged vacancies are passivated by hydrogen. The intellectual merit of this Phase-I proposal relies on the utilization of Doppler broadening of electron-positron annihilation radiation and electric and magnetic field-dependent gated Hall-bar measurements. These techniques will provide a fundamental understanding of defect types, concentrations, and their interactions with hydrogen atoms, enabling the design of an optimized passivation technique.