Modification of the surface properties of PbSnTe$\langle$In$\rangle$ epitaxial layers with composition near band inversion

High-resistance Pb$_{1-x}$Sn$_{x}$Te$\langle$In$\rangle$ layers grown by molecular beam epitaxy on BaF$_2$(111) substrates with compositions close to band inversion have been investigated. The I–V characteristics and relaxation dependences of the photocurrent of the structures in dependence on the chemical surface treatment and subsequent exposure of the samples in air have been examined. It has been observed that the characteristics significantly transform depending on the physicochemical surface state. It has been found that the chemical surface treatment in the hydrochloric acid solution in isopropyl alcohol leads to an increase in the current by up to four orders of magnitude with the subsequent recovery of the I–V characteristics upon exposure of the samples in air for several days.