Electrical characteristics of electroless gold contacts on p-type Hg1−xCdxTe

High contact resistance of the order of 10−3 Ω cm2 observed in p-type HgCdTe is one of the practical problems in the production of fine pitch high operating temperature and avalanche photodiode detector array. Electrical and compositional measurements on Au/p-HgCdTe are reported to understand the difficulties in reducing the contact resistance in HgCdTe detectors. Characterization of Au contacts on p-type Hg1−xCdxTe (x=0.3) formed by electrode-less (electroless) process and current transport mechanism are discussed. SIMS depth profiling of interfacial layer formed by the reaction of gold chloride with HgCdTe have been analyzed. Extent of the interfacial layer containing Au, Te, O and Cl is found to increase with increasing deposition time. Effect of annealing on the migration of Au across the contact region and electrical characteristics are presented. Heavily doped HgCdTe region with NA=1017 cm−3 is produced beneath the contact regions after annealing at 80 °C leading to an order of magnitude improvement in the specific contact resistance. These results are useful for the creation of Au/p-HgCdTe contacts in a controlled and reproducible manner.