Semi-insulating CCl4-doped InP grown at low temperature by LP-MOCVD

Growth at low temperature has become a common technique for producing semi-insulating III-V compound and alloy materials. The generally accepted mechanism for the semi-insulating behavior in arsenic-containing materials is the annealing-induced formation of precipitates of the excess arsenic that is incorporated during growth. These precipitates act as Schottky barriers that are buried in the surrounding lattice of single-crystal material, capturing free carriers. Several groups have attempted to grow epitaxial semi-insulating InP at low temperature using molecular beam epitaxy (solid phosphorus source) and gas-source molecular beam epitaxy (GSMBE, PH₃ as the phosphorus source). Garcia, et al. have observed incorporation of 1 to 3 excess at.% of P in epitaxial layers grown by GSMBE at temperatures of 170 to 200°C. After this material was annealed at temperatures around 600°C, precipitates of alpha-white cubic P with diameters of 3 to 7 nm were found uniformly distributed throughout the epitaxial layer. Despite these similarities in structural properties between low-temperature-grown GaAs and InP, undoped LT-InP exhibits n-type conduction with the conductivity increasing as growth temperature decreases. This conductivity has recently been attributed to the presence of a P-antisite-related donor level that lies above the conduction band. In this paper, we demonstrate low-temperature epitaxial growth of semi-insulating InP by low-pressure metalorganic chemical vapor deposition (LP-MOCVD), accomplished by the introduction of CCl₄ vapor into the growth chamber. The material exhibits resistivities on the order of 10⁹ Ω cm and is single crystalline, as determined by double-crystal x-ray diffraction measurements. Carbon, hydrogen, and chlorine incorporation as measured by secondary ion mass spectrometry (SIMS) increases as the CCl₄ flow rate is increased (which may explain the semi-insulating behavior of the material)