器件结构和材料质量对GaAs MESFET噪声系数的影响

本文从栅源串联电阻R_s和有效栅长L_f两方面论述了深槽自对准斜蒸栅结构可明显减小R_s与缩短L_f,有利于降低器件的噪声系数。 本文还用相关栅长L_a和器件在低温下的性能说明GaAs材料的质量对器件噪声系数的影响。提高GaAs半绝缘衬底和缓冲层质量以及与有源层交界面附近的迁移率,可较明显地缩短相关栅长L_a,降低器件噪声。 采用这一器件结构,并选用质量较高的GaAs材料,制得的MESFET,在12GHz下相关增益G_a为7.5dB,噪声系数NF_(min)为1.4dB,与理论预计值相符。

Effects of Device Structure and Material Quality on Noise Figure of GaAs MESFETs

This paper discusses the deep recess self-aligned, oblique-evaporation gate structure in terms of the gate-source series resistance Rs and the effective gate length Lf. This structure can considerably reduce R, and shorten Lf, which is advantageous to reduce the noise figure of devices. The effect of the quality of GaAs material on the noise figure of devices is also explained using the associated gate length La and the performance of devices at low temperature. The improvements of quality of GaAs semi-insulating substrate, the buffer layer and the carrier mobility near the boundary plane of the active layer may distinctly shorten the associated gate length La and reduce the noise of devices. MESFETs with this device structure and fine GaAs material exhibit the associated gain (Ga) of 7.5dB and the minimum noise figure (NFmin) of 1.4dB at 12GHz, which are in good agreement with theoretical values.