Self-Heating Characterization of SiGe:C HBTs by Extracting Thermal Impedances

In this letter, the self-heating effects in SiGe heterojunction bipolar transistors (HBTs) and the influence of the emitter width
$W_{E}$
and the emitter length
$L_{E}$
on all of the thermal parameters are presented for the first time by extracting the thermal resistance
$R_{\rm TH}$
, capacitance
$C_{\rm TH}$
, and time constant
$T_{\rm TH}$
. First, we discuss the thermal impedance extraction method. The approach is based on both dc and ac measurements within the 30 kHz–6 GHz low-frequency range. Then, the self-heating influences of various SiGe HBT topologies are presented. Finally,
$R_{\rm TH}$
,
$C_{\rm TH}$
, and
$T_{\rm TH}$
, which were extracted from different transistor geometries, are compared.