氮掺杂对氢终端金刚石射频器件特性的影响

采用微波等离子体化学气相沉积(MPCVD)技术,通过改变气源中的氮含量,得到不同结晶质量的单晶金刚石,通过激光切割以及抛光控制样品尺寸为5 mm×5 mm×0.5 mm,然后对样品进行表面氢化处理并研制了金刚石射频器件,系统研究了氮含量对金刚石材料晶体质量和金刚石射频器件性能的影响。随着氮含量的增加,虽然单晶金刚石生长速率有所增加,但是其拉曼半峰全宽(FWHM)、XRD摇摆曲线半峰全宽也逐渐增加,光致发光光谱中对应的NV缺陷逐渐增多,晶体结晶质量逐渐变差,不仅导致沟道载流子的迁移率出现退化,而且也使金刚石射频器件出现了严重的电流崩塌和性能退化问题。通过降低氮浓度,提升材料的结晶质量,沟道载流子迁移率得到显著提升,金刚石射频器件的电流崩塌得到有效抑制,电流增益截止频率f_T和功率增益截止频率f_max分别从17 GHz和22 GHz大幅度提升至32 GHz和53 GHz。

Effect of Nitrogen Doping on the Perfomances of the Hydrogen Terminated Diamond RF Transistors

The microwave plasma chemical vapor deposition technology was employed to grow the single crystal diamond substrates with different crystalline qualities by changing the nitrogen content in the gas source. The sample size was controlled at 5 mm×5 mm×0.5 mm by laser cutting and polishing. The surfaces of diamond substrates were hydrogenated and the diamond RF transistors were fabricated on them. The influence of the nitrogen content on the crystalline quality of the diamond and the performance of the device has been systematically studied. With the increase of the nitrogen content, although the growth rate of the single crystal diamond increases, the FWHM of Raman and XRD rocking curves, as well as the corresponding NV defects in the photoluminescence spectra also gradually increases, indicating that the crystalline quality became worse, which not only degrade the carrier mobility of the channels, but also make the diamond RF transistor suffer from the problems of current collapse and performance degradations. By reducing the nitrogen content and improving the crystalline quality of the diamond, the carrier mobility significantly increases, the current gain cutoff frequency f_T and power gain cutoff frequency f_max significantly increases from 17 GHz and 22 GHz to 32 GHz and 53 GHz, respectively.