Surface morphology of SiO_2 coated InP/InGaAs/InGaAsP microstructures following the irradiation with ArF and KrF excimer lasers

摘要

Successful fabrication of devices from quantum well-intermixed material requires efficient control of its surface morphology. To address this problem, we have employed atomic force microscopy to study surface morphology of InP/InGaAs/InGaAsP QW microstructure coated with d_(SlO2) = 50, 150, 190, 243 and 263 nm thick SiO_2 films. Both ArF (193 nm) and KrF (248 nm) excimer lasers have been used to irradiate series of samples with up to 400 pulses of fluence 76 to 156 mJ/cm2. The roughness (σ_(rms)) of SiO_2 layer after both lasers irradiation and RTA decreases as the pulse number increases. Following RTA, a smoother surface morphology was observed for all irradiated samples. The cap InP layer was found to have a relatively smaller roughness (~ 0.4 nm) due to the protection provided by the SiO_2 layer during excimer laser irradiation and high temperature RTA. For samples coated with 50- or 150-nm-thick SiO_2 and irradiated by the ArF laser, the blueshift is only obtained when the SiO_2 layer was ablated. However, the sample coated with 243-nm-rnthick SiO_2 (d_(Slo2)≈λ(KrF) following the 75-pulse-irradiation with the KrF laser at 124mJ/cm~2 and RTA, showed a smooth surface (σ_(RMs) = 1.8 nm) and maximum blueshift of 74 nm achieved without removal of the SiO_2 layer.