Deep levels in p-type GaAs grown by metalorganic vapor phase epitaxy

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Abstract
We report a detailed deep level transient spectroscopic study in p‐type Mg‐ and Zn‐doped GaAs epitaxial layers grown by metal‐organic vapor phase epitaxy. Dependence of deep level structures on doping concentrations and growth temperatures has been investigated. Over a wide range of growth conditions, four hole traps and an electron trap ranging in activation energy from 0.18–0.79 eV were measured in GaAs:Mg while only a single hole trap has been observed in GaAs:Zn.The presence of a certain trap and its concentration in GaAs:Mg depends mainly on the doping concentration in the layers. The total trap concentration in the GaAs:Mg decreases rapidly with doping concentration for p>4×1017 cm−3. The physical and chemical origins of several of these traps have been identified. The Mg‐doped GaAs always exhibited a greater concentration of midgap trap levels than the Zn‐doped material, regardless of dopant concentration or growth temperature. The overall defect structure and dopant incorporation characteristics indicate that Zn is the preferred dopant species.