Infrared absorption of deep defects in molecular-beam-epitaxial GaAs layers grown at 200 °C: Observation of an<i>EL</i>2-like defect

Abstract

Infrared optical absorption and Hall-effect techniques were employed to study deep defects in As-rich molecular-beam-epitaxial GaAs layers grown at very low temperature (200 \ifmmode^\circ\else\textdegree\fi{}C). A large ir absorption band was observed between 0.55 eV and the band edge. This band is composed of photoquenchable and photounquenchable components. Photoquenching, thermal recovery from the metastable state, and ir absorption properties of the quenchable defect, of estimated concentration of \ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}${10}^{18}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$, are identical to those of EL2. On the other hand, the unquenchable defect, of estimated concentration \ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}${10}^{19}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$, resembles the isolated ${\mathrm{As}}_{\mathrm{Ga}}$ antisite observed in neutron-irradiated GaAs. Both defects' concentrations, which show different isothermal annealing behavior are reduced by about an order of magnitude upon thermal annealing at 600 \ifmmode^\circ\else\textdegree\fi{}C for 10 min. This reduction is accompanied by an increase of sample resistivity by a few orders of magnitude.