A. Kameyama et al., ANALYSIS OF DEVICE PARAMETERS FOR PNP-TYPE ALGAAS GAAS HBTS INCLUDINGHIGH-INJECTION USING NEW DIRECT PARAMETER EXTRACTION/, I.E.E.E. transactions on electron devices, 44(1), 1997, pp. 1-10
Device parameters of the small-signal T equivalent circuit for pnp-typ
e AlGaAs/GaAs heterojunction bipolar transistors (HBT's) are obtained
using a new direct parameter extraction technique. These parameters ar
e analyzed not only under the low-current conditions but also under hi
gh-current conditions so as to understand the RF-performance fall-off
after Base Pushout occurs. In this analysis, the intrinsic and extrins
ic small-signal parameters which affect RF performance are directly de
termined using several steps without numerical optimization in order t
o properly analyze device parameters. The T equivalent circuit model d
etermined by the method shows excellent agreement with the mean errors
of 3.56.9% under both low-and high-current conditions. The analysis s
howed that the intrinsic transit time, which is the sum of the base tr
ansit time (tau(b)) and the collector depletion layer transit time (ta
u(c)), small-signal emitter resistance (r(e)), small-signal base resis
tance (r(b)) and collector-base capacitance (C-BC) all increase under
high-current conditions. In addition, we found that the intrinsic tran
sit time is the dominant parameter for the fall-off of the cut-off fre
quency (ft) under high-current conditions, and there is little effect
of r(b) and C-BC in the fall-off of the maximum oscillation frequency
(f(t)) under high-current conditions. Judging from these results, devi
ce parameters are successfully obtained under a wide current range by
a new parameter extraction technique and circuit modeling for HBT's un
der a wide current range can be achieved using the small-signal T-equi
valent circuit.