Effect of p and n doping on neutral impurity and SiO₂ dielectric cap induced quantum well intermixing in GaAs/AlGaAs structures

We report the diffusion and quantum well intermixing (QWI) effects of the neutral impurities fluorine and boron in p- and n-type AlGaAs in the GaAs/AIGaAs system. Boron was found to show significant diffusion in p-doped AlGaAs material but only exhibited a very small amount of diffusion in n-doped material after furnace annealing. Boron was found to retard intermixing in p-AlGaAs. This may be due to the existence of interstitial B, which may reduce the native group III interstitial concentration. The mechanism of boron impurity-induced disordering (IID) in n-AlGaAs was proposed to be attributed to both the diffusion of point defects generated during ion implantation and the Fermi level effect from the deep acceptor B^-_As. Extremely fast fluorine diffusion rates, which may be correlated to an interstitial diffusion mechanism, have been observed. Results from fluorine UD suggest the possibility of the ionization of fluorine which gives rise to a higher electron concentration during annealing, leading to higher degrees of intermixing in n-AlGaAs. The intermixing rate of impurity free vacancy disordering (IFVD) using an SiO₂ cap was found to be higher in n-type and intrinsic AlGaAs than in p-type AlGaAs, which suggests that the diffusion of the group III vacancy is inhibited in p-type material which has a higher group III interstitial concentration. These results imply that n-i-p structures should be more effective than conventional p-i-n structures for the IFVD process.