中文摘要：

分析了GaN HFET大信号工作特性随器件漏压、栅压、栅长和工作频率变化的实验特征,发现器件的射频输出功率和功率附加效率随频率升高、漏压增大和栅长缩短而下降的规律及在3mm波段短栅长的高截止频率场效应管没有输出功率的现象。从场效应管电极边界条件出发导出了势垒层的解析表面势及其微商,研究了表面势随漏压、栅压和栅长的变化。通过自洽能带计算求出了不同漏压、栅压和栅长下的能带和电子状态。研究了GaN HFET射频工作中产生的能带畸变。从不同漏压、栅压和栅长变化下的能带畸变出发,提出了沟道电子状态随栅压、漏压和栅长变化的GaN HFET大信号射频工作模型。用此大信号模型解释了实验中观察到的高频、大功率器件特性及3mm瓶颈。提出了研发大功率GaN HFET的新见解。

英文摘要：

The large signal behavior of GaN HFET as a function of drain voltage,gate voltage,gate length and frequency is analyzed in this paper,from which it is found that the output power and PAEare decreased as frequency increases,drain voltage rises,and gate length shortens,and the short gate length GaN HFETs with high cut-off frequency couldn′t give useful output power.An analytical surface potential and its derivative for the barrier layer of GaN HFET are derived from the electrode boundary conditions of HFET,from which the surface potential varying with drain voltage,gate voltage,and gate length is investigated.Through the self-consistent solution of hetero-conjunction energy band,the electron states and energy bands for different drain voltages,gate voltages and gate lengths are calculated.The energy band deformation during the RF operation is deeply analyzed.From the band deformation under different drain voltages,gate voltages,and gate lengths,a large signal operation model for GaN HFET is proposed,where the electron states in channel vary with the drain voltages,gate voltages and gate lengths.By using this large signal operation model,the large signal operation behaviors and the bottleneck in 3mm band GaN HFET mentioned above are explained,from which a new point of view for developing large power GaN HFET is proposed.