氧化鋯與氧化鎵穿隧奈米結構載子傳輸分析

Abstract

本研究製作以氧化鋯( ZrO₂）與氧化鎵（Ga₂O₃）為主體之穿隧奈米結構（Tunneling Nanostructure）元件，並於非對稱雙能障量子井結構（Double Barrier Quantum Well, DBQW）中，探討載子穿隧傳輸機制與電性特徵。採用垂直堆疊之多層結構，將氧化鋯、氧化鎵與氧化銦錫（Indium Tin Oxide, ITO）等薄膜組成主體，並以氧化鎵包覆側壁，以有效抑制側向漏電流並提升垂直導電特性。元件製程採用濕蝕刻技術，成功製作最小直徑為5 微米之元件，並於皮安培（pA）電流等級下觀察到階梯狀之穿隧電流特徵。 本研究展示準束縛態能階對齊條件下之穿隧行為；然而於陷阱密度較高之元件中，則觀察到其導電特性主要受到陷阱輔助穿隧（Trap-Assisted Tunneling, TAT）機制影響，與穿隧特性表現存在顯著差異。為深入探討傳輸行為，吾人應用熱發射（Thermionic Emission）理論評估材料介面間之能障高度，並以轉移矩陣法（Transfer Matrix Method, TMM）建立穿透係數模型，模擬其於不同電場條件下之變化，據以進行理論與實驗之對應分析與驗證。

This study presents a tunneling nanostructure device, primarily composed of zirconium oxide (ZrO₂) and gallium oxide (Ga₂O₃), and implemented in an asymmetric double barrier quantum well (DBQW) structure, to analyze carrier tunneling transport mechanisms and electrical characteristics. The device adopts a vertically stacked multilayer architecture comprising ZrO₂, Ga₂O₃, and indium tin oxide (ITO) thin films. Sidewalls passivation with Ga₂O₃ effectively suppresses lateral leakage currents and enhances vertical conduction. Utilizing wet etching techniques, devices with a minimum diameter of 5 μm were successfully fabricated, exhibiting step-like tunneling current features at the picoampere (pA) level. The observed stepwise current behavior is attributed to tunneling under aligned quasi-bound state conditions. However, in devices with higher trap densities, conduction characteristics were predominantly governed by trap-assisted tunneling (TAT), deviating significantly from ideal tunneling behavior. To further elucidate the transport mechanisms, thermionic emission theory was employed to extract interfacial barrier heights, and a transmission coefficient model was developed using the transfer matrix method (TMM) to simulate field-dependent variations. Theoretical analyses were correlated with experimental results for comprehensive validation.