Hydrogenation of ZnS passivation for HgCdTe

The physical and electrical effects of exposing ZnS passivation to a H₂/CH₄ reactive ion etch (RIE) plasma are examined. Using secondary ion mass spectrometry (SIMS) and capacitance-voltage (CV) analysis, hydrogen is shown to penetrate through the ZnS and accumulate on the ZnS side of the ZnS/HgCdTe interface, causing a reduction in the positive fixed charge density, possibly due to binding at sulphur vacancy sites. CV results show a reduction in the average and spread of fixed interface charge (Q_f), however the interface trap density (Qit) is unchanged. With a 2 hour 80°C bake, SIMS profiles indicate a change in the ZnS/HgCdTe interface with movement of H, Cd, Hg and Te species.