Interaction of deep-level traps with the lowest and upper conduction minima in InP

Abstract

Deep‐level electron traps in bulk, vapor‐phase epitaxial (VPE) and liquid‐phase epitaxial (LPE) undoped InP crystals are investigated by an extensive method of capacitance measurement. Eight different traps are found in bulk and VPE crystals, and on the other hand no traps are found in LPE crystals. Characteristics of three traps with emission activation energies of ΔE_e=0.43, 0.59, and 0.63 eV are analyzed in detail. The absolute energy levels for these traps measured from the lowest Γ conduction minimum are E_T=0.34, 0.20, and 0.24 eV, respectively. It is shown that the 0.43‐eV trap is coupled to the Γ minimum and that the 0.59‐ and 0.63‐eV traps are coupled to the upper L minima. The capture of Γ electrons by the 0.43‐eV trap is found to exhibit a thermally activated capture cross section σ with a barrier energy of ΔE_B=0.09 eV. On the contrary, the temperature dependence of capture of L electrons by the 0.59‐eV trap is found to be dominated by the temperature dependence of electron density in the L minima and to exhibit a negligible ΔE_B for σ. The intervalley energy separation ΔE_LΓ?0.39 eV is derived and found consistent with the observed emission and capture properties of both of the L‐coupled traps. Reasonable agreements are obtained between the capture cross sections derived from capture and from emission experiments, for both the Γ‐coupled and L‐coupled traps, respectively.