The study of the optical properties of the GaAs with point defects

GaAs is a common material for negative electron affinity photoelectric cathodes. It has a widely application in night vision. It is unavoidable to produce point defects in the process of the GaAs growth. In this article, the first principle method is used to calculate the formation energy and the optical properties of six types familiar point defects in GaAs. Three types of point defects (Ga vacancy defect, As antisite defect and As interstitial defect) are easier to be formed in these six types according to the formation energy calculation. In fact, crystal GaAs is grown in an As-rich environment. The Ga vacancy, As antisite and As interstitial defects are easier to be formed in reality. Hence the theoretical calculation results are in keeping with the experiments. In this article, the optical properties of these three types are compared with that of perfect GaAs. The electron structures are changed as a result of the point defects. Some of the defect levels enter into the band gap and the electron transitions become easier. It makes the optical spectra move to the low-energy region. Additionally, GaAs with Ga vacancy defect and that with As interstitial defect shows similar optical properties. Therefore both of the two types of defects can be considered as the same in the later experiments. The theoretical results in this article provide the basis for experimental study for photoelectric emission of the real GaAs material related to the optical properties and electronic structures.