Disordering of InGaAs/GaAs multi-quantum well structure by impurity-free vacancy diffusion for advanced optoelectronic devices and their integration

We studied the impurity-free vacancy diffusion (IFVD) of In _0.2Ga_0.8As/GaAs multi-quantum well (MQW) structures for advanced optoelectronic devices and their integration. To gain deeper insight in IFVD, the influence of the plasma enhanced chemical vapor deposition parameters, such as SiH₄ flow rate, deposition temperature, deposition pressure and rf power, of SiO_x and SiN_x capping layers on the band gap energy shift induced by IFVD was investigated. We observed that the magnitude of the blue shift increases with the decrease of SiH₄ flow rate for SiO_x and SiN_x capping layers. The blue shift of the PL peak energy increases greatly with the increase of deposition pressure and slightly with the decrease of deposition temperature. The influence of rf power was found to be negligible. All these dependences are related to the porosity in the dielectric capping layers in the QW intermixing. We fabricated the wavelength shifted ridge-waveguide InGaAs/GaAs MQW lasers with 967, 946 and 927 nm emission wavelengths that have undergone IFVD using SiO₂ capping layers at different annealing temperatures of 850, 900 and 950 °C, respectively. Also, multi-wavelength InGaAs/GaAs MQW lasers by the area-selective IFVD using different stoichiometric SiO_x capping layers were studied. The lasing wavelength difference of about 31 nm is obtained between the ridge-waveguide laser diodes fabricated with the MQWs that had undergone the same thermal treatments using the SiO_x film provided with SiH₄ flow rates of 20 and 300 sccm.