The role of lattice matching in improving the performance of PbSnTe IR photodiodes

The role of lattice matching in determining the quantum efficiency of heterostructure PbSnTe photodiodes has been investigated. It has been established that a mismatch of less than 2 × 10^-4results in a photodiode with quantum efficiency of ∼ 43%, very close to the maximum 50% possible without an anti-reflection coating. This compares with a value of 28% reported in the case of a heterojunction with a mismatch of 4 × 10^-3. The increase in the quantum efficiency is attributed to the high crystalline quality at the heteroface and its vicinity in the lattice-matched system, in contrast to a high defect density found in the mismatched system.