Annealing-induced evolution of defects in low-temperature-grown GaAs-related materials

Abstract

Infrared absorption spectroscopy, optical transient current spectroscopy (OTCS), and photoluminescence (PL) spectroscopy are used to investigate the annealing induced evolution of defects in low-temperature (LT)-grown GaAs-related materials. Two LT samples of bulk GaAs (sample A) and ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ multiple-quantum-well (MQW) structure (sample B) were grown at 220 and 320 \ifmmode^\circ\else\textdegree\fi{}C on (001) GaAs substrates, respectively. A strong defect-related absorption band has been observed in both as-grown samples A and B. It becomes weaker in samples annealed at temperatures above 600 \ifmmode^\circ\else\textdegree\fi{}C. In sample A, annealed in the range of 600--800 \ifmmode^\circ\else\textdegree\fi{}C, a large negative decay signal of the optical transient current (OTC) is observed in a certain range of temperature, which distorts deep-level spectra measured by OTCS, making it difficult to identify any deep levels. At annealing temperatures of 600 and 700 \ifmmode^\circ\else\textdegree\fi{}C, both ${\mathrm{As}}_{\mathrm{Ga}}$ antisite and small As cluster-related deep levels are identified in sample B. It is found that compared to the As cluster, the ${\mathrm{As}}_{\mathrm{Ga}}$ antisite has a larger activation energy and carrier capture rate. At an annealing temperature of 800 \ifmmode^\circ\else\textdegree\fi{}C, the large negative decay signal of the OTC is also observed in sample B. It is argued that this negative decay signal of the OTC is related to large arsenic clusters. For sample B, transient PL spectra have also been measured to study the influence of the defect evolution on optical properties of LT ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ MQW structures. Our results clearly identify a defect evolution from ${\mathrm{As}}_{\mathrm{Ga}}$ antisites to arsenic clusters after annealing.