GeSe/准二维电子气氧化物范德华异质结中陷阱态工程调控的光电导特性

Photoconductivity Modulated by Trap-State Engineering in GeSe/Quasi-2DEG Oxide Van Der Waals Heterojunctions

摘要: 本工作采用机械剥离与氩离子束辅助轰击技术，成功制备了由p型GeSe与n型氧化物准二维电子气(Q2DEG)组成的范德华异质结，并系统研究了其在20 K低温下的光响应特性。结果表明，光电流随入射光波长的减小而增大，即短波长激发下光响应更强，且器件在循环测试中表现出稳定且可重复的响应行为。在20 K下，本征载流子的热激发被显著抑制，光生非平衡载流子被界面缺陷陷阱俘获，产生明显的持久光电导效应。施加反向偏压可有效提取陷阱中的俘获载流子，且反向放电电流随偏压扫描速率的增大而增加。进一步通过逐步提高反向偏压幅度的连续放电测量，观察到释放电流随偏压幅度逐级增大的现象，揭示了外电场与陷阱势垒深度之间的直接物理关联，为通过宏观电学测量表征氧化物基异质界面陷阱态的能量分布提供了可行途径。本研究深化了对氧化物基异质结中界面陷阱电荷动力学的理解，并为基于界面陷阱工程的功能性光电器件设计开辟了新方向。

Abstract: In this work, we successfully fabricated a van der Waals heterojunction composed of p-type GeSe and n-type oxide quasi-two-dimensional electron gas (Q2DEG) using mechanical exfoliation combined with argon ion beam bombardment. The photoresponse characteristics of the device are systematically investigated at 20 K. The results show that the photocurrent increases with decreasing incident light wavelength, i.e., a stronger photoresponse is observed under shorter-wavelength excitation, and the device exhibits stable and reproducible response under cyclic testing. At 20 K, thermal excitation of intrinsic carriers is strongly suppressed, and photogenerated nonequilibrium carriers are captured by interfacial defect traps, giving rise to a pronounced persistent photoconductivity effect. Applying a reverse bias can efficiently extract the trapped carriers from the traps, and the reverse discharge current increases with the bias sweep rate. Furthermore, sequential discharge measurements with progressively increasing reverse bias amplitude reveal an increase of the released current with increasing bias amplitude, uncovering a direct physical correlation between the applied electric field and the trap barrier depth. This correlation provides a feasible pathway to characterize the energy distribution of trap states at oxide-based heterointerfaces via macroscopic electrical measurements. This study deepens the understanding of interfacial trapped charge dynamics in oxide-based heterojunctions and opens new avenues for the design of functional optoelectronic devices based on interfacial trap engineering.