Deep Level and Near-Band-Edge Recombination in Semiconducting Antiperovskite Hg_3Se_2I_2 Single Crystals

摘要

The wide-bandgap, semiconducting ternary compound Hg_3Se_2I_2 has shownpromise as room-temperature hard-radiation detector. Since this compoundwas first reported, there has been significant improvement in crystal growthusing a chemical vapor transport method with a polyethylene growth agent.To study the effects of this additional precursor on crystal quality, the natureof radiative and nonradiative defects using photoluminescence (PL) andphotocurrent (PC) studies of Hg_3Se_2I_2 single crystals are investigated. Incontrast to earlier studies, excitation intensity-dependence of PL emissionshows that the near-band-edge (NBE) emission bands are all excitonic innature. The PL intensity decreases with increasing temperature, with thehigher energy peaks quenching by 40 K and the deeper levels quenchedafter 110 K. The PC spectra show a complex structure at room temperaturerelated to NBE transitions in the band structure, while at low temperatureonly the direct gap transition is observed due to phonons freezing out. ThePC spectra at low temperature also indicate several midgap levels that areattributed to native defects within the bulk crystal. These results indicatethat the high quality of Hg_3Se_2I_2 single crystals is maintained when thetransport agent is used during growth, although there are still a variety ofdefects present.