Growth and optical characteristics of Mg-doped GaAs epitaxial layers by molecular beam epitaxy

Photoluminescence (PL) measurement is used to study the optical properties of Mg-doped GaAs epitaxial layers grown by molecular beam epitaxy (MBE) with various growth temperatures. Four dominant PL peaks are observed, which may be associated with free-to-bound (e–A), exciton-bound to neutral acceptor (AoX), and two kinds of acceptor associated (g, g–g) transitions. The g and g–g peaks are especially prominent in a sample with a carrier concentration of 2.3 × 1017 cm−3. To investigate the behavior of each peak as a function of temperature, PL measurements were carried out over a temperature range of 18–152 K. The AoX peak position follows the Varshni model for GaAs with increasing temperature. For the g and AoX peaks, we observe an increase in PL intensity with increasing temperature from 18 to 28 K. This phenomenon is known as “negative thermal quenching (NTQ)”, and it is observed in the g peak for the first time in this paper.

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► Four photoluminescence peaks are observed in Mg-doped GaAs.
► The temperature dependent PL intensities for the four peaks are investigated.
► The PL intensities of the acceptor related peak (g) and the transition of an exciton bound to neutral acceptor peaks show negative thermal quenching.
► This phenomenon was occurred by the other peaks’ dissociation and carriers’ trapping.