The high frequency and noise performance ( $T_{\mathrm {MIN}}$ , NF_MIN, $R_{n}$ , and $Z_{\mathrm {sopt}}$ ) of SiGe heterojunction bipolar transistors (HBTs) are characterized for the first time from dc and $S$ -parameter measurements up to 70 GHz and from 2 to 400 K. Significantly improved current gain ~10 000, minimum noise temperature, $T_{\mathrm {MIN}}$ (< 1 K below 8.5 GHz), MAG, $f_{T}$ (458 GHz), and $f_{\mathrm {MAX}}$ (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, $J_{\mathrm {OPT}}$ , increases with temperature, following the crossover between shot noise and thermal noise. In contrast, the peak- $f_{T}$ and peak- $f_{\mathrm {MAX}}$ current densities increase by more than 50% at 2 K, likely due to the higher $v_{\mathrm {sat}}$ . A decrease in BV_CEO, 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- $f_{T}$ current.

中文翻译：

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从直流到 70 GHz 和低至 2 K 的 SiGe HBT 的高频和噪声性能的低温表征

高频和噪声性能（ $T_{\mathrm {MIN}}$, NF_最小值, $R_{n}$， 和 $Z_{\mathrm {sopt}}$) 的 SiGe 异质结双极晶体管 (HBT) 首次从直流和 $新元- 高达 70 GHz 和 2 至 400 K 的参数测量。电流增益显着提高 ~10 000，最低噪声温度， $T_{\mathrm {MIN}}$（< 1 K，低于 8.5 GHz），MAG， $f_{T}$（458 GHz），和 $f_{\mathrm {MAX}}$（534 GHz）在 2 K 和 300 K 下观察到，没有杂质去离子的证据。发现最佳噪声系数电流密度， $J_{\mathrm {选择}}$，随着散粒噪声和热噪声之间的交叉，随温度增加。相比之下，峰 $f_{T}$和峰值- $f_{\mathrm {MAX}}$电流密度在 2 K 时增加了 50% 以上，可能是由于较高的 $v_{\mathrm {sat}}$. _{BV CEO}下降，预期由于较高的电流增益和负输出电导在 2-200 K 范围内观察到在高于峰值的大电流下的直流输出特性 $f_{T}$当前的。