Sharp Exciton Photoluminescence in Low-Temperature-Grown GaAs/AlGaAs Multiple Quantum Wells

Abstract

We demonstrate the fabrication of high-quality GaAs/AlGaAs multiple quantum wells (MQWs) at very low temperature by solid-state source molecular beam epitaxy. The key to our method is to maintain a critical arsenic pressure or As/Ga beam equivalent pressure ratio to ensure a sharp heterointerface and a low defect density. A sharp heavy-hole excitonic photoluminescence (PL) signal was observed from the MQWs with a well width of 7.5 nm and a barrier width of 4 nm grown at 360°C. The PL linewidth of the QW heavy-hole exciton is 3 meV measured at 77 K. This emission linewidth is far narrower than that in a sample with the same structure grown at the standard growth temperature. The resistivity of the as-grown sample is about 5×106 Ωcm and increases to 5×107 Ωcm after postgrowth annealing at 700°C. The low growth temperature and high optical quality as well as the high resistivity make this kind of material suitable for use in ultrafast optical and monolithic integrated optoelectronic devices.