The Preparation And Morphology Of Quantum Polycyclic Rings On GaAs (001) Surface

In recent years,quantum rings have attracted extensive attention from physicists due to their unique physical properties.In concentric quantum rings,charge tunneling between different angular momentum states is strongly suppressed due to selection rules.Concentric quantum rings can effectively couple direct and indirect excitons,so concentric quantum rings can be applied to the research of semiconductor quantum computing devices.The physical properties of quantum rings are closely related to their morphologies and the dispersion of exciton energy varies with the radius of the rings.In this paper,the quantum double ring was made by two-step heating method and the quantum tricyclice ring was made by three-step heating method.The effects of the deposition amount,deposition rate and crystallization As pressure of Ga droplets on the quantum double ring;And the effects of As pressure and growth temperature on the quantum tricycle was studied.The two-step heating method : First,close the As valve and deposit 10 MLs Ga droplets at the substrate temperature of 430,then the substrate temperature below toin As equivalent beam pressure of Pa crystallization under the condition of 20 s;Substrate temperature from to,the same As equivalent beam pressure crystallization for 10 minutes.The experimental results show that the two-step heating method can be used to prepare quantum double rings.The research on the growth conditions shows that with the increase of Ga atomic deposition,the diameter of the inner and outer ring of the quantum double ring increases,the height of the inner ring increases,and the height of the outer ring decreases.With the increase of Ga atomic deposition rate,the diameter of the inner and outer ring of the quantum double ring becomes smaller,the height of the inner ring becomes lower,the height of the outer ring increases,and the density of the quantum double ring increases.The reasons for these phenomena are explained in this paper.The three-step heating method: As first the substrate temperature to,deposite of Ga droplets under the zero As pressure;The second step,the substrate temperature from to in As equivalent beam pressure ofPa crystallization under the condition of 20 s;The third step,shut down As valve and make the substrate temperature from to,the same As equivalent beam pressure to crystallizating 20 s.The fourth step,shut down As valve,temperature to,when temperature reached open As valve,in the same As equivalent beam pressure crystallization for 10 min.Experimental results show that As the As beam increases,the final nanostructure changes from a double ring to a triple ring and finally to a single ring.The increase of temperature makes the shape of the ring more obvious,the diameter of the ring increases and the height of the ring decreases.At the same time,we found that when the temperature difference between adjacent growth temperatures is very large,the quantum four rings will be formed.This paper analyzes the causes of these phenomena and gives the ring forming mechanism of the third ring and the fourth ring.