The high frequency and noise performance ( TMINT_{\mathrm {MIN}} , NFMIN, RnR_{n} , and ZsoptZ_{\mathrm {sopt}} ) of SiGe heterojunction bipolar transistors (HBTs) are characterized for the first time from dc and SS -parameter measurements up to 70 GHz and from 2 to 400 K. Significantly improved current gain ~10 000, minimum noise temperature, TMINT_{\mathrm {MIN}} (< 1 K below 8.5 GHz), MAG, fTf_{T} (458 GHz), and fMAXf_{\mathrm {MAX}} (534 GHz) are observed at 2 K compared to 300 K, with no evidence of impurity deionization. It is found that the optimum noise figure current density, JOPTJ_{\mathrm {OPT}} , increases with temperature, following the crossover between shot noise and thermal noise. In contrast, the peak- fTf_{T} and peak- fMAXf_{\mathrm {MAX}} current densities increase by more than 50% at 2 K, likely due to the higher vsatv_{\mathrm {sat}} . A decrease in BVCEO, expected due to the higher current gain, and negative output conductance are observed in the 2–200 K range in the dc output characteristics at large currents above the peak- fTf_{T} current.

中文翻译：

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SiGe HBT 从 DC 到 70 GHz 以及低至 2 K 的高频和噪声性能的低温特性


SiGe 异质结双极晶体管 (HBT) 首次从直流和SS 参数测量频率高达 70 GHz，温度范围为 2 至 400 K。电流增益显着提高~10 000，最低噪声温度，TMINT_{\mathrm {MIN}}（< 1 K 低于 8.5 GHz）、MAG、fTf_{T } (458 GHz) 和 fMAXf_{\mathrm {MAX}} (534 GHz) 在 2 K 与 300 K 下观察到，没有杂质去离子的证据。研究发现，随着散粒噪声和热噪声之间的交叉，最佳噪声系数电流密度 JOPTJ_{\mathrm {OPT}} 随着温度的增加而增加。相比之下，峰值 fTf_{T} 和峰值 fMAXf_{\mathrm {MAX}} 电流密度在 2 K 时增加超过 50%，这可能是由于 vsatv_{\mathrm {sat}} 较高。由于电流增益较高，预计 BVCEO 会下降，并且在高于峰值 fTf_{T} 电流的大电流下，直流输出特性在 2–200 K 范围内观察到负输出电导。