Effects of As pressure on optical features of low-temperature grown GaAs/AlGaAs multiple quantum wells

Abstract

Photoluminescence (PL) spectroscopy is measured to study the optical features of GaAs/Al 0.3Ga 0.7As multiple quantum wells grown at low temperature (LT) about 350°C by molecular beam epitaxy. Under an As-rich condition, different As pressures are used during the growth of different samples. It is found that, the full-width at half-maximum (FWHM) of PL peaks is improved at first with the decrease of As pressure. However, it degrades owing to the appearance of shallow-level related emission peak when the As pressure is lowered further. For annealed samples, the changes of their PL features reveal that Ga vacancy ( V Ga) in the LT-samples can be controlled precisely by As pressure used during the growth whereas the influence of As pressure on As antisites (As Ga) becomes significant only when As pressure is higher than 3.0×10 −7 Torr. The strong dependence of PL features on As pressure is attributed to the different control effect of As pressure for V Ga and As Ga. After the optimization of As pressure, the sample with sharp PL peak and high resistivity is obtained. The FWHM of PL peak is 3.1 meV and can be compared with that of normal temperature grown sample with same structure. The result agrees well with the growth dynamics and compensation mechanism between shallow level and deep level.