Deep levels in as-grown and Si-implanted In0.2Ga0.8As–GaAs strained-layer superlattice optical guiding structures

Abstract

Trap levels in ∼2‐μm In_0.2Ga_0.8As (94 Å)/GaAs(25 Å) strained‐layer superlattices, suitable for optical waveguides, have been identified and characterized by deep‐level transient spectroscopy and optical deep‐level transient spectroscopy measurements. Several dominant electron and hole traps with concentrations ∼10¹⁴ cm⁻³, and thermal ionization energies ΔE_T varying from 0.20 to 0.75 eV have been detected. Except a 0.20‐eV electron trap, which might be present in the In_0.2Ga_0.8As well regions, all the other traps have characteristics similar to those identified in molecular‐beam epitaxial GaAs. Of these, a 0.42‐eV hole trap is believed to originate from Cu impurities and the others are probably related to native defects. Upon Si implantation and halogen lamp annealing, new deep centers are created. These are electron traps with ΔE_T=0.81 eV and hole traps with ΔE_T=0.46 eV. Traps occurring at room temperature may present limitations for optical devices.