GaN基p-i-n型紫外探测器钝化工艺研究

GaN-based p-i-n Type UV Detector Passivation Process Study

摘要:

钝化层膜系的选择及其工艺的优化对降低GaN基紫外探测器的漏电流和提升其可靠性是至关重要的。文章采用多种钝化层:等离子体增强化学气相沉积生长的Si₃N₄ (PECVD-Si₃N₄)、电感耦合等离子体化学气相沉积生长的Si₃N₄ (ICPCVD-Si₃N₄)和SiO₂ (ICPCVD-SiO₂)以及等离子原子层沉积生长的Al₂O₃ (PEALD-Al₂O₃),分别制备了GaN基金属-绝缘体-半导体(MIS)器件,并对MIS器件的电流-电压(I-V)和电容-电压(C-V)特性进行了对比研究。采用PECVD-Si₃N₄作为钝化层的GaN基MIS器件具有较低的漏电流；在双层PECVD-Si₃N₄钝化层中插入PEALD-Al₂O₃薄膜可以进一步降低界面态密度:平均界面态密度从3.94×10¹³eV-1·cm-2降低到3.52×10¹¹eV-1·cm-2。利用这种“三明治结构”钝化膜,制作p-i-n型GaN基紫外雪崩探测器,与单层膜系的探测器相比,在113V反向偏压下的暗电流从3.73×10-8A降至3.34×10-8A。

Abstract:

In order to reduce the leakage current and improve the reliability of GaN-based UV detectors, the selection of the passivation layer film system and the optimization of its process are crucial. In this paper, GaN-based metal-insulator-semiconductor (MIS) devices were prepared using the following passivation layers:Si₃N₄ grown by plasma-enhanced chemical vapor deposition (PECVD), Si₃N₄ and SiO₂ grown by inductively coupled plasma chemical vapor deposition (ICPCVD), and Al₂O₃ grown by plasma atomic layer deposition (PEALD), respectively. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the devices were studied comparatively. It is found that when the PECVD-grown Si₃N₄ was used as the passivation layer, it has a lower leakage current in GaN-based MIS devices; by introducing a layer of PEALD-grown Al₂O₃ into the double-layer PECVD-grown Si₃N₄ passivation layer, the interfacial state density is further reduced:the average interfacial state density decreases from 3.94×10¹³eV-1·cm-2 to 3.52×10¹¹eV-1·cm-2. Using this passivation film with "sandwich structure", a p-i-n type GaN-based UV avalanche detector was fabricated. The dark current at 113V reverse bias is reduced from 3.73×10-8A to 3.34×10-8A compared with the detector of the Si₃N₄ film system without PEALD-grown Al₂O₃.