Persistent photoconductivity in Ho-doped InGaAsP epitaxial layers

Persistent photoconductivity (PPC) was investigated in Ho-doped InGaAsP epilayers with Ho concentrations in the range of 0–0.15wt%. The decay behavior of PPC resembles that of AlxGa1−xAs and can be well described by a stretch-exponential function. The temperature-dependent PPC studies show that the lattice relaxation of DX-like centers is responsible for the PPC effect. As the Ho doping increases, the decay-time constant and the electron-capture barrier were found to decrease. We suggest that the introduced Ho elements may chemically react with donor impurities, suppressing lattice relaxation and hence reducing the electron-capture barrier. Also, rare earth doping is demonstrated to be an effective method of improving the quality of InGaAsP epilayers.