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 (A ^oX), 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 A^oX peak position follows the Varshni model for GaAs with increasing temperature. For the g and A^oX 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.