ArF excimer laser-induced quantum well intermixing in dielectric layer coated InGaAs/InGaAsP microstructures

Abstract

It has been known that excimer laser irradiation of surfaces of III-V quantum well (QW) semiconductor microstructures can be used for selective area bandgap engineering of such materials [1]. Depending on the laser used, investigated microstructure and the irradiation environment both enhanced quantum well intermixing (QWI) leading to blue shifting of the bandgap energy [2], as well as suppressed QWI [3] processes have been reported. Excimer lasers are attractive for bandgap engineering as they can be used to pattern large size wafers, often in a single step, and without the need of using photolithography masks that normally are required to achieve selective area processing.To investigate the role of the solid environment and the influence of laser-induced surface defects on the amplitude of the QWI process, we have investigated InP/InGaAs/InGaAsP QW microstructure coated with 2 sets of SiO2 layers having distinctively different optical properties. An ArF (193 nm) laser has been used to irradiate a series of samples with up to 400 pulses of fluence 76 mJ/cm2. The bandgap shift of irradiated sites, following two 120 sec rapid thermal annealing steps at 650°C and 675°C, varies with the pulse fluence and number. A maximum of 120 nm blueshift of the bandgap was observed for the samples irradiated with 150 pulses of the laser. We have also investigated the ArF laser QWI on the QW microstructure coated with layers of Si3N4. We discuss the advantages of this approach for post growth fabrication of multibandgap QW material suitable for designing and manufacturing of monolithically integrated photonic devices.It has been known that excimer laser irradiation of surfaces of III-V quantum well (QW) semiconductor microstructures can be used for selective area bandgap engineering of such materials [1]. Depending on the laser used, investigated microstructure and the irradiation environment both enhanced quantum well intermixing (QWI) leading to blue shifting of the bandgap energy [2], as well as suppressed QWI [3] processes have been reported. Excimer lasers are attractive for bandgap engineering as they can be used to pattern large size wafers, often in a single step, and without the need of using photolithography masks that normally are required to achieve selective area processing.To investigate the role of the solid environment and the influence of laser-induced surface defects on the amplitude of the QWI process, we have investigated InP/InGaAs/InGaAsP QW microstructure coated with 2 sets of SiO2 layers having distinctively different optical properties. An ArF (193 nm) laser has been used to irradiate a series...