Annealing-induced evolution of defects in low-temperature-grown GaAs-related materials - art. no. 115324

Infrared absorption spectroscopy, optical transient current spectroscopy (O TCS), and photoluminescence (PL) spectroscopy are used to investigate the a nnealing induced evolution of defects in low-temperature (LT)-grown GaAs-re lated materials. Two LT samples of bulk GaAs (sample A) and GaAs/AlxGa1-xAs multiple-quantum-well. (MQW) structure (sample B) were grown at 220 and 32 0 degreesC on (001) GaAs substrates, respectively. A strong defect-related absorption band has been observed in both as-grown samples A and B. It beco mes weaker in samples annealed at temperatures above 600 degreesC. In sampl e A, annealed in the range of 600-800 degreesC, a large negative decay sign al 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 an d 700 degreesC, both As-Ga antisite and small As cluster-related deep level s are identified in sample B. It is found that compared to the As cluster, the As-Ga antisite has a larger activation energy and carrier capture rate. At an annealing temperature of 800 degreesC, the large negative decay sign al 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 th e, defect evolution on optical properties of LT GaAs/AlxGa1-xAs MQW structu res. Our results clearly identify a defect evolution from AS(Ga) antisites to arsenic clusters after annealing.