Ternary Pb1−xCdxSe films grown by molecular beam epitaxy on GaAs/ZnTe hybrid substrates

Abstract

Thin epitaxial Pb1−xCdxSe films with cadmium content x ≤ 0.36 have been grown by molecular beam epitaxy (MBE) on highly resistive, lattice matched (0 0 1) ZnTe/GaAs hybrid substrates. The High Resolution X-ray Diffraction (HRXRD) indicates that the films crystallize in the rock salt structure. Up to x = 0.12 the Pb1−xCdxSe films are (0 0 1) oriented and monocrystalline with negligible amount of other phases. The lattice constant of the films decreases proportionally to the Cd content. As evidenced by low-temperature photoluminescence (PL) the energy gap of Pb1−xCdxSe films increases with the increasing Cd content. The parameters of optical phonons and plasmons in the material are established by infrared reflectance measurements. The most interesting property of the Pb1−xCdxSe films is revealed by classical transport measurements. The alloying of PbSe with CdSe reduces the hole concentration in the material from a typical value of 3 × 1018 cm−3 in the pure PbSe film down to 3 × 1016 cm−3 in the film containing x = 0.052 of Cd. The reduction of the hole concentration by two orders of magnitude makes the Pb1−xCdxSe films very attractive for infrared detector applications. Simple photoresistors made of Pb1−xCdxSe films exhibit sensitivity to the infrared radiation up to the room temperature.