Er-related deep centers in GaAs doped with Er by ion implantation and molecular beam epitaxy

Abstract

Deep level transient spectroscopy (DLTS) and temperature-dependent Hall effect measurements were performed on undoped, n-, and p-type GaAs doped with Er either by ion implantation or during molecular beam epitaxial (MBE) crystal growth. For light Er doping (≲1017 cm−3), a hole trap was observed at 35 meV above the valence band, whereas for heavier doping (≳5×1017 cm−3), a hole trap was observed at 360 meV. Both traps were found in both ion implanted and MBE materials. The 35 meV center is attributed to the Er atom occupying the Ga site and acting as an isovalent impurity, whereas the 360 meV center is attributed to Er in an interstitial position. Furthermore, photoluminescence and DLTS measurements of Er-implanted GaAs revealed that both the Er3+ intra-4f-shell emission intensity and concentration of the deep 360 meV centers were maximized at an annealing temperature of 750 °C, and they decreased at higher temperature anneals, while the concentration of the shallow 35 meV centers increased.