MONOLITHIC INTEGRATION OF OPTOELECTRONIC DEVICES USING QUANTUM WELL INTERMIXING

摘要

Quantum-well intermixing (QWI) can shift the bandgap and refractive index of quantum-well (QW) materials after their growth is completed. Our studies of QWI focused on impurity-free vacancy diffusion (IFVD) in the InGaAs/GaAs/AlGaAs material system. The IFVD process consists of two steps, namely deposition of a capping layer on the sample surface, followed by rapid thermal annealing (RTA). In our experiments aiming at selection of appropriate materials for enhancement or inhibition of QWI, QW samples were capped with single layers of either spin-on glass (SOG) or MgF_2. Room-temperature photoluminescence (PL) spectra were taken before and after RTA. Blue-shift of the PL peak wavelength provides direct evidence that QWI occurred, and can be conveniently used to evaluate the degree of intermixing. We show that SOG capping accelerates interdiffusion, while MgF_2 acts as QWI inhibitor. Together, these two materials can then be used to achieve spatially selective QWI required in monolithic integration of optoelectronic devices.