Characterization and Control of Interaction between Quantized Energy Levels and Surface/Interface States in Compound Semiconductor Quantum Structures.

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The purpose of the research is to investigate an interaction between the quantized energy levels and the surface/interface states in compound semiconductor quantum structures, and to investigate the applicability of the novel silicon-intelayr based passivation technique to passivation of compound semiconductor quantum structures. The main results are summarized below.(1) It has been shown that the photoluminescence (PL) intensity from the near-surface AlGaAs/GaAs quantum wells (QWs) decreases exponentially with decreasing the thickness of the top AlGaAs barrier layr below 10nm, and that this PL reduction is due to the interaction between the quantized QW enegy levels and the surface states.(2) The novel passivation technique for compound semiconductor surfaces was successfully developed, in which an ultrathin silicon/Si_3N_4 double-layr is utilized as a interface control layr (ICL).(3) A drastic reduction of interface state density into the 2*10^<10>cm^<-2> was obtained for the InGaAs MIS system by application of the novel passivation technique. This value is the lowest reported so far for the compound semiconductor MIS systems.(4) The novel passivation process was applied to passivation of Al_<0.3>Ga_<0.7>As/GaAs/Al_<0.3>Ga_<0.7> As near-surface Qs. Complete recovery of the PL intensity was achieved with an observed maximum recovery factor of 1000. The recovery of PL intensity can be explained by reduction of interface state densities by the novel passivation process, resulting in reduction of non-radiative surface recombination via tunneling processes. The present passivation technique can be applicable to surface/inteface control of compound semiconductor quantum structures.