Effects of annealing on TlGaAs/GaAs single hetero structures and TlGaAs/GaAs multiple quantum well structures grown by low-temperature MBE

Annealing studies were performed on single hetero (SH) structures and multiple quantum well (MQW) structures of TlGaAs/GaAs grown by molecular-beam epitaxy (MBE) at a low growth temperature of 190 °C. X-ray diffraction (XRD) measurements on the SH structures revealed that the mole fraction of the antisite As in the low-temperature grown layers can be decreased to less than 0.1% by annealing at 450 °C for 30 min. Due to this annealing, however, decrease and inhomogeneity in Tl mole fraction were also caused. On the other hand, extending the total time of annealing at 400 °C to 16 h enabled us to decrease the antisite As mole fraction to about 0.1% without causing decrease and inhomogeneity in Tl mole fraction. It has also been confirmed that the well-defined MQW structures of TlGaAs/GaAs remain almost unchanged after annealing at 400 °C for 30 min.