原子层沉积Al2O3/n-GaN MOS结构的电容特性

摘要

The Ni/Au/Al2O3/n-GaN metal-oxide-semiconductor structure with circular transparent electrode has been fabricated by using atomic layer deposition technique. Effects of ultra-violet (UV) light illumination on the capacitance characteristics and deep interface states are analyzed. Physical origin of bias-induced capacitance drop in the accumulation region of some non-ideal devices is explored. Due to the extremely long electron emission time and the extremely slow minority carrier generation rate, a typical deep depletion behavior can be observed in the dark room-temperature capacitance-voltage sweep curve, and the deep-level interface state occupancy above the electron quasi-Fermi level remains unchanged. Under the UV illumination, photo-induced holes will empty the deep interface traps above the electron quasi-Fermi level, and also de-charge the deep donor-like traps in the oxide layer. The anomalous capacitance drop in the accumulation region is attributed to the bias-dependent excessive leakage conductance across the dielectric layer, which might be induced by a“charge-to-breakdown”process related to electrical traps in the oxide and the inferior interface quality.%利用原子层沉积技术制备了具有圆形透明电极的Ni/Au/Al2O3/n-GaN金属-氧化物-半导体结构，研究了紫外光照对样品电容特性及深能级界面态的影响，分析了非理想样品积累区电容随偏压增加而下降的物理起源。在无光照情形下，由于极长的电子发射时间与极慢的少数载流子热产生速率，样品的室温电容-电压扫描曲线表现出典型的深耗尽行为，且准费米能级之上占据深能级界面态的电子状态保持不变。当器件受紫外光照射时，半导体耗尽层内的光生空穴将复合准费米能级之上的深能级界面态电子，同时还将与氧化层内部的深能级施主态反应。非理想样品积累区电容的下降可归因于绝缘层漏电导的急剧增大，其诱发机理可能是与氧化层内的缺陷态及界面质量有关的“charge-to-breakdown”过程。