GaSe/InSe Heterojunction Device Electrical Storage And Optical Storage Characteristics

Two-dimensional materials exhibit novel physical and chemical properties due to their unique structural characteristics,such as valley-spin,quantum Hall effect,and nonlinear optics,and are widely used in field effect transistors,solar cells,photodetectors and other fields.In addition,because there are no dangling bonds on the surface of the two-dimensional material,there is no need to consider the problem of lattice mismatch when combining with other materials.Different two-dimensional materials can be stacked to form a van der Waals heterostructure,and the charge transfer and band arrangement at the interface can be used.Further broaden the functionality of two-dimensional nanomaterials.Based on this,this article takes the representatives of Group III-VI compounds—InSe and Ga Se as the research object to construct GaSe/InSe and Ga Se/BN/InSe heterojunction devices.By studying their electrical and optoelectronic properties,they are found to be collector storage devices,permanent photocurrent and negative light guide are integrated to realize the versatility of the device,combined with the charge transfer and energy band arrangement at the interface,reveal the mechanism of electrical storage,permanent photocurrent and negative light guide.GaSe/InSe heterojunction devices have stable electrical storage performance.When V_bg-max=60 V,the width of the hysteresis window can reach（ΔV）72.53 V,and the amount of stored charge（ΔQ）is 5.21×10¹² cm^-2 When it reaches 2000 s,the on-off ratio is 10³,and the storage state can be controlled by applying different pulse bias voltage.For Ga Se/BN/InSe heterojunction devices,when V_bg-max=50 V,the width of the hysteresis window（ΔV）is 14.12 V,and the amount of stored charge is 1.01×10¹² cm^-2.When it reaches 500 s,the switching ratio is Only 10,much smaller than GaSe/InSe heterojunction devices.In order to better explain the electrical storage mechanism and explore the electrical storage performance of GaSe/InSe heterojunction devices at different temperatures,at 64 K,when V_bg-max is 60 V,the change in hysteresis window（ΔV）is 40.29V,The amount of charge that can be stored（ΔQ）is 2.89×10¹² cm^-2,and the on-off ratio is10⁶ when it reaches 1000 s.When the temperature rises to 400 K,when V_bg-max is 50 V,the change in hysteresis window（ΔV）is 76.86 V,and the amount of stored charge（ΔQ）is 5.52×10¹² cm^-2.When it reaches 500 s,it turns on-off ratio is 10.This electrical storage property is caused by the energy band bending caused by the applied pulse bias and the charge transfer:in the low resistance state（Low Resistance,LRS）,the bias voltage of-60 V is applied,and the energy band of Ga Se and InSe is downward.Bending,the potential barrier is reduced,the electron transitions,and the current is large;in the high resistance state（High Resistance,HRS）,a bias of+60 V is applied,the energy bands of Ga Se and InSe bend upward,the potential barrier increases,and the electrons are pinned,The current is small.In addition,temperature has an important effect on the charge transfer at the interface.As the temperature increases,the amount of effectively stored charge decreases,and the switching ratio decreases.GaSe/InSe heterojunction devices have a permanent photocurrent phenomenon under the excitation of a high-resistance 532 nm light source.The on-off ratio is 10⁴.After2000 s,the current only drops by 6.89 n A.Different pulse bias voltages are applied to control the optical power density and light.The number of cycles can effectively control the light storage state.Ga Se/BN/InSe heterojunction devices also have a permanent photocurrent phenomenon.After 500 s,the current drops only by 0.30 n A,and the on-off ratio is less than 10,which is far lower than GaSe/InSe heterojunction devices.When the808 nm light source is selected for excitation,the permanent photocurrent phenomenon still exists when the GaSe/InSe heterojunction device is in a high resistance state.In order to better explain the optical storage mechanism,we explored the influence of different temperatures on the optical storage performance of GaSe/InSe heterojunction devices,and found that the permanent photocurrent phenomenon still exists in the high resistance state at 100 K,and the on-off ratio is 10⁶.After 1000 s,the current drops by1.63μA.When the temperature rises to 350 K,the permanent photocurrent phenomenon still exists,the switching ratio is 100,and the current drops by 84.0 n A after 1200 s.The reason for the above phenomenon is that after a+60 V pulse is applied,the energy bands of Ga Se and InSe will bend upward,electron pinning induces negative charges on the Si O₂/Si substrate,and the energy band will bend downward at this time.There will be a lot of holes in the valence band of InSe.When excited by a light source,the holes in InSe move to Ga Se.However,due to the large number of holes in the valence band of InSe,when the light source is turned off,the holes in InSe will still move to Ga Se,resulting in a permanent photocurrent phenomenon.Interestingly,at low temperatures,GaSe/InSe heterojunction devices exhibit negative photoconductivity in the low-resistance state.It is found that the downward trend of the current is affected by the optical power density,and the current declines slowly at low power;and when the optical power increases,the current decline speed becomes faster.When the 808 nm light source is selected for excitation,the negative light guide phenomenon still exists.The reason is:when a-60 V pulse bias is applied to a GaSe/InSe heterojunction device,the energy bands of Ga Se and InSe bend downwards,the potential barrier is reduced,and the electrons in the Ga Se conduction band transition to the conduction band of InSe.,Positive charge is induced on the Si O₂/Si substrate,and the energy bands of Ga Se and InSe are both bent upward.Under the excitation of a 532 nm or 808 nm light source,the photogenerated electrons in the InSe conduction band tunnel into the conduction band of Ga Se and recombine with the holes in the valence band,resulting in a negative photoconductivity phenomenon.When the power increases,more electrons in InSe tunnel to Ga Se,which increases the probability of recombination with holes,resulting in a faster current drop.