设计并研制了一种新型复合沟道Al0.3Ga0.7N/Al0.05Ga0.95N/GaN HEMT(CC-HEMT)微波单片集成压控振荡器(VCO),且测试了电路的性能.CC-HEMT的栅长为1μm,栅宽为100μm.叉指金属-半导体-金属(MSM)变容二极管被设计用于调谐VCO频率.为提高螺旋电感的Q值,聚酰亚胺介质被插入在电感金属层与外延在蓝宝石上GaN层之间.当CC-HEMT的直流偏置为Vgs=-3V,Vds=6V,变容二极管的调谐电压从5.5V到8.5V时,VCO的频率变化从7.04GHz到7.29GHz,平均输出功率为10dBm,平均功率附加效率为10.4%.当加在变容二极管上电压为6.7V时,测得的相位噪声为-86.25dBc/Hz(在频偏100KHz时)和-108dB/Hz(在频偏1MHz时),这个结果也是整个调谐范围的平均值.据我们所知,这个相位噪声测试结果是文献报道中基于GaN HEMT单片VCO的最好结果.

A novel structure composite-channel Al0.3Ga0.7N/Al0.0 Ga0.95N/GaN HEMT (CC-HEMT) microwave monolithic integrated circuit voltage-controlled oscillator (VCO) was designed, fabricated and characterized. The CC-HEMT has 1 μm × 100 μm gate. The inter-digitated metal-semiconductor-metal (MSM) varactor is used to tune the frequency of VCO. The polyimide dielectric layer is inserted between the major metal traces and GaN buffer to improve Q factor of spiral inductors.The VCO exhibits frequency range between 7.04 ～ 7.29GHz with varactor voltage from 5.5V to 8.5V and average output power of 10dBm and average efficiency of 10.4% at bias gate of -3V and bias drain of 6V. The measured phase noise is-86.25dBc/Hz and -108dBc/Hz at offset frequency of 100 kHz and 1 MHz at varactor voltage (Vtune) of 6.7V. This is almost average phase noise in the range of tuning frequency. To our knowledge, this is the best reported phase noise for GaN monolithic GaN HEMT VCO.