SiO2 passivation and ionic-liquid gating for (In,Ga)As-InP narrow channels

Narrow channels mesa-etched from an In_0.75Ga_0.25As-InP heterostructure are passivated using SiO₂ films prepared by sputtering for the protection concerning the negligible surface depletion. Concerning the scattering for the electrons caused by the molecules attached to the side walls, the conduction becomes nearly independent of the atmosphere in which the channels are placed. The incompleteness in preventing the alteration of surface conditions may suggest diffusion of plausibly oxygen through the SiO₂ film. The channel resistance decreases anomalously for temperatures above 250 K, indicating that defects are generated in the deposition of the SiO₂ layer. The thermal activation of the defect-induced conduction can be eliminated by annealing. Nevertheless, the recovery of the crystallinity is not sufficient for heavy damages due to the decomposition of InP at high annealing temperatures. Although the existence of degenerate electrons cannot be deduced from the temperature dependence of the resistance, low-temperature quantum magnetotransport properties provide the evidence. Besides, gate-tuning of the channel resistance using a solid-type ionic liquid is additionally demonstrated.