Phosphorus-Vacancy-Related Deep Levels in Gainp Layers Grown by Molecular Beam Epitaxy

Abstract

Deep levels in lattice matched Ga 0 . 51 In 0 . 49 P/GaAs heterostructure have been investigated by thermal-electric effect spectroscopy(TEES) and temperature dependent conductivity measurements. Four samples were grown by molecular beam epitaxy with various phosphorus (P 2 ) beam equivalent pressure(BEP) of 0.125, 0.5, 2, and 4x10" 4 Torr. We report for the first time, to our knowledge, an electrical observation of phosphorus vacancy point defects in the GaInP/GaAs material system. The phosphorus vacancies , Vp. behave as an electron trap which is located at EC-0. 28 +0. 0 2 eV. We have found that this trap dominates the conduction band conduction when T> 220K, and is responsible for the variable-range hopping conduction when T < 220K. Its concentration decreases with the increasing phosphrous BEP. Successive rapid thermal annealing showed that its concentration increases with the increasing annealing temperature. Another electron trap at EC-0.5leV was also observed only in samples with P 2 BEP less than 2x10-4 Torr. Its capture cross section is 4.5x10" 15 cm 2 as obtained from the illumination time dependent TEES spectra.