Cryogenic Characterization of the High Frequency and Noise Performance of SiGe HBTs From DC to 70 GHz and Down to 2 K
IEEE Microwave and Wireless Components Letters(2022)
摘要
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.
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关键词
Cryogenic temperatures,heterojunction bipolar transistor (HBT),noise,semiconductor device modeling,silicon germanium,terahertz
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