GaN基异质结缓冲层漏电分析

通过对GaN基异质结材料C-V特性中耗尽电容的比较，得出AlGaN/GaN异质结缓冲层漏电与成核层的关系.实验结果表明，基于蓝宝石衬底低温GaN成核层和SiC衬底高温AlN成核层的异质结材料比基于蓝宝石衬底低温AlN成核层异质结材料漏电小、背景载流子浓度低.深入分析发现，基于薄成核层的异质结材料在近衬底的GaN缓冲层中具有高浓度的n型GaN导电层，而基于厚成核层的异质结材料的GaN缓冲层则呈高阻特性.GaN缓冲层中的n型导电层是导致器件漏电主要因素之一，适当提高成核层的质量和厚度可有效降低GaN缓冲层的背景载流子浓度，提高GaN缓冲层的高阻特性，抑制缓冲层漏电. 关键词： AlGaN/GaN异质结 GaN缓冲层 漏电 成核层

Analysis of the leakage current in GaN-based heterostructure buffer layer

The relations between the buffer leakage current and the characteristics of nucleation layer of AlGaN/GaN heterostructure have been obtained by comparative study of depletion capacitance of C-V characteristics in GaN-based heterostructure. The results showed that, the heterostructure material based on a sapphire substrate with a low-temperature GaN nucleation layer and SiC substrate with a high-temperature AlN nucleation layer have smaller buffer leakage current and lower carrier concentration of the background GaN buffer layer than that based on a sapphire substrate with a low-temperature AlN nucleation layer. A thorough analysis shows that, there is an n-type GaN conductive layer near the GaN/substrate interface in buffer layer based on the thinner nucleation layers. Contrarily, high resistivity GaN buffer layers appear in heterostructure materials based on thicker nucleation layer. One of the main causes of device leakage is the n-type GaN conductive layer. Appropriately improving the quality and thickness of nucleation layer can effectively reduce the carrier concentration, raise the resistivity and suppress the leakage current of the GaN buffer layer.