Limits in growing TlGaAs/GaAs quantum-well structures by low-temperature molecular-beam epitaxy

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

“…The appearance of the Tl droplets on these two samples grown under the higher Tl BEPs is because of the moderate As BEP used in this study [5]. If higher As BEPs had been adopted, we could obtain samples without Tl droplets on their surfaces, as has been shown in another study of ours [4].…”

“…We however adopted such a moderate As BEP in this study in order to obtain layers with not so high concentrations of antisite As at the sacrifice of Tl droplet appearance. On the other hand, it has been already proved in our previous study [5] that TlGaAs/GaAs MQW structures can be grown successfully even at such a moderate As BEP as long as each TlGaAs well layer is thin enough.…”

“…r Tl x Ga 1Àx As has been proposed as a new material for infrared detectors [1], lasers [2], and field effect transistors [3]. In our previous studies, we have succeeded by lowtemperature (LT) molecular-beam epitaxy (MBE), not only in growing a TlGaAs single layer of 7% in Tl mole fraction [4], but also in growing a TlGaAs/GaAs multiple quantum well (MQW) structure of 9% in Tl mole fraction and 5 nm in thickness of TlGaAs well layers [5]. It has, however, been revealed that the LT-grown TlGaAs contains a large amount of antisite As as in LT-grown GaAs [6].…”

“…The samples of the SH structures used in this study (S003, S007, and S008) were those grown in our previous study [5]. In each growth of the SH structures, a GaAs buffer layer was grown on a GaAs (0 0 1) substrate at 580 1C for 30 min after the removal of native oxide.…”

“…The MQW samples used here (M008-22 and M009-22) were those grown in our previous study [5]. In the growth of these MQW samples, the cell temperatures of Ga and As were, respectively the same as in the growth of the SH structures.…”