Download RF-and Noise-Modeling of Semiconductor devices based on InP

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RF-and Noise-Modeling of Semiconductor devices based on InP
Silja Ehrich, Michael Agethen*, Wolfgang Brockerhoff, Franz-Josef Tegude
Solid-State Electronics Department, Gerhard-Mercator-University Duisburg
Lotharstr. 55, 47057 Duisburg, Germany; Tel. +49 203 379 3881, [email protected]
*IPAG-Innovative Processing AG, Duisburg, Germany
ABSTRACT
In this work we focus on consistent small-signal and rf-noise parameter models of on InP based devices. S-parameter
and rf-noise parameter modeling show excellent performance of the models used. Of main interest are the intrinsic
noise sources, because these give information about the physically relevant noise phenomena of the intrinsic devices.
Additionally, the experimental set-up for s-parameter as well as rf-noise parameter measurements is presented.
MEASUREMENT SET-UP
Fig. 1 shows a typical measurement set-up, which allows s-parameter and rf-noise parameter characterization of twoport-devices. The measurement set-up comprises the noise figure meter (HP8970B) as central unit and the calibrated
noise source (HP346A) [1]. The noise figure test-set (HP8971) and the synthesizer (HP8672A) are necessary to down
convert the measurement frequency to a frequency range of 10MHz to 1600MHz, which the noise figure meter is able
to directly process. To determine the four noise parameters of interest (Fmin, Rn, GS,opt and BS,opt) of a linear two-port
device the noise figures at various generator reflection coefficients ΓSi have to be measured.
These particular reflection coefficients can be set using a commercial electronic tuner sub-system. This consists of the
control unit (NP5), the mismatch noise source (MNS), including the actual tuner, and the remote receiver module
(RRM) with an integrated low noise pre-amplifier. Additionally, both elements (MNS and RRM) contain rf-switches
which are necessary for system calibration. Furthermore, these switches enable the simultaneous measurement of the
noise and the corresponding scattering parameters in a frequency range of 1GHz up to 18GHz.
The complete system is controlled by a computer system which allows the evaluation of the data and the extraction of
the specific noise parameters from the measured noise figures [1].
HP 8510C Network Analyzer
Computer System
HP 8510C Bussystem
HP 83650A
Synthesizer
HP 8517A Test-Set
HP 8970B Noise Figure Meter
HP 8672A Synthesizer
HP 4142B
Parameter-Analyzer
HP 8971 Noise Figure Test-Set
RF-Cable
NP5 Control Unit
HP 346A
Noise Source
MNS
alessi
Alessi-Prober
Fig. 1: Measurement Set-up
RRM
HP 8970B Bussystem
HP 715/50 Workstation
IEEE-488
Bussystem
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RF-NOISE MODELS
The models used are based on extended temperature noise models. In case of narrow band noise, equivalent noise
temperatures are associated to all resistances. As usual the small-signal model is divided into two parts, an intrinsic and
an extrinsic one. The extrinsic resistances only add thermal noise, consequently their equivalent noise temperature is set
to the ambient temperature TA. Fig. 2 and fig. 3 show the rf-noise-parameter models, the extrinsic noise effects are
specified by declaring the noise temperature TA to each extrinsic resistance. The intrinsic part is described in more
detail replacing all noisy resistances with their one-port noise equivalent circuit, a noise current source in parallel or a
noise voltage source in series to the now noise free resistance.
RF-Noise Model of InAlAs/InGaAs/InP-HFET
Fig. 2 shows a typical intrinsic equivalent rf-noise model for InAlAs/InGaAs/InP-HFET [2], which takes into account
the influence of gate-leakage current on rf- as well as noise performance. Gate-leakage is modeled by the additionally
included resistances Rpgd and Rpgs. Moreover, this model considers the effects due to impact ionization [2]. This is
enabled by an additional voltage controlled current source gm,im a RC combination in parallel to the output resistance.
The current source is controlled by the voltage drop across the high field region at the drain-end of the gate which is
equal to the drain-gate-voltage vdg. The distinctive frequency dependence of the impact ionization effects on rf- and
noise behavior, resp., are described by the combination of Rim and Cim. For noise modeling purpose an additional white
noise source iim is included parallel to the current source gm,im. This arrangement of noise source and RC combination
characterizes the frequency dependence of the externally available noise current iim,ext.
C IO
intrinsic HFET
G
RG
v dg
Cgd
LG
T=TA
LD
R pgd
vg
T=0K
R
pgs
T=0K
Rgs
T=0K
C gs
RD
iim
Rd
T=0K
ip
C im
Cd
id
D
T=TA
Rim
T=0K
v
CIN
C OUT
LS
RS
e- j
gm
gmim . v dg
v
T=TA
S
S
Fig. 2: Consistent small-signal and rf-noise parameter model of InAlAs/InGaAs/InP-HFET.
RF-Noise Model of InGaAs/InP-HBT
Fig. 3 shows the extended small-signal equivalent circuit of a HBT, which builds up the basis of the consistent smallsignal and rf-noise parameter model. This “T”-like equivalent circuit can easily be found considering the typical threemesa design of III-V semiconductor based HBT [3]. The noise from the included RC-combination RBP and CBP at the
base contact (fig. 3), taking into account a frequency dependence of the non alloyed ohmic base contact, is assumed to
be thermal noise.
C IO
C fb
C jc
B
RB
T=TA
LB
CBP
ibb
i
i cc
LC
i jc
R BP
T=TA
R bb
T=0K
R jc
T=0K
C IN
R cc
T=0K
RC
T=TA
C
C OUT
i je
R je
C je
T=0K
LE
RE
E
T=TA
E
Fig. 3: Consistent small-signal and rf-noise parameter equivalent circuit of InP/InGaAs HBT.
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RF-PARAMETER MODELING
For modeling the rf-parameters, all equivalent circuit elements (small-signal elements and equivalent noise
temperatures) are optimized using evolutionary optimization strategies [4-5]. These strategies combine deterministic
and stochastic search algorithms, so these approaches are independent of the initial optimization values. Evolutionary
optimization has demonstrated its performance in high dimensional optimization problems and results in the global
optimum. The small-signal equivalent elements are extracted by small-signal modeling and maintained during noiseparameter optimization. Only the intrinsic noise equivalent temperatures are optimized.
Modeling the HFET
Fig. 4 shows the measured and the modeled s-parameter data in a frequency range from 45 MHz up to 40 GHz. The
symbols represent the measured data, the solid lines the modelled values. The results of the measured and modeled rfnoise parameters (minimum noise figure Fmin, equivalent noise resistance Rn and optimum generator reflection
coefficient Γopt) of the HFET are given in fig. 5 to fig. 7.
Due to the Lorentzian shape of the external short-circuit noise current iim.ext, corresponding to a upper frequency band
limitation especially at low frequencies, a strong impact on the noise performance can be observed. The phenomenon of
impact ionization now leads to an increase of the minimum noise figure Fmin. Especially the increase of the minimum
noise figure at low frequencies reflects the influence of the impact ionization process. In contrast to the influence of a
gate-leakage current, impact ionization leads to higher optimum generator impedances and causes a strong increase of
the equivalent noise resistance Rn at low frequencies, as well.
Also bias dependent measurements are conducted. Therefore the drain-source voltage is kept constant and the gatesource voltage is varied. An increase of VGS leads to an increase of all noise-parameters.
In case of noise resistance Rn the bias dependence at low frequencies is significant. But the agreenment between
measured and modeled data is still very good.
1.0
0.4
-j1.0
4
-j0.
.0
-j2
2.0
0.1
8.0
optimum generator reflection coefficient Γopt
Fig. 4: Measured (symbols) and modeled (lines) sparameters at VDS = 1.8 V; VGS = -0.2 V(s11 and s22 in
Smith-Chart, s12 and s21 in polar diagram).
Fig. 6: Measured (symbols) and modelled (lines) optimum
generator refection coefficient Γopt
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norm. equiv. noise resistance Rn/Z0
2.0
minimum noise figure Fmin
dB
3
2
1
0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0
2
4
6
8
10
frequency f
12
14
GHz
18
Fig. 5: Measured (symbols) and modelled (lines) minimum
noise figure
0
2
4
6
8
10
12
frequency f
14
GHz
18
Fig. 7: Measured (symbols) and modelled (lines) normalized
equivalent noise resistance rn = Rn/Z0
Modeling the HBT
The excellent capability of the model used to describe s-parameters of HBT in the whole measured frequency range up
to 40 GHz is shown in fig. 8. Here, the measured and modelled s-parameters within the active device region are
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presented. Bias dependent measurements are performed and good agreement between measured and modelled data was
achieved.
To prove the consistency with rf-noise parameter modelling, fig. 9 to fig. 11show the measured and modelled rf-noise
parameters for three different bias conditions at constant collector-emitter voltage VCE = 1.2 V and various collector
currents from IC = 1 mA up to IC = 20 mA.
First of all the excellent agreement between measured and modelled data can clearly be seen for all noise parameters.
For the minimum noise figure Fmin, a strong increase with rising collector current is obvious (fig. 9). The normalized
equivalent noise resistance rn = Rn/Z0 (fig. 11) shows the same dependence on collector current IC. A minor influence of
the collector current is found for the optimum generator reflection coefficient Γopt (fig. 10).
0.4
2.0
0.4
1.0
16.0
collector current IC
1 mA
10 mA
20 mA
4
-j0.
.0
-j2
-j1.0
optimum generator reflection coefficient Γopt
Fig. 8: Measured (symbols) and modelled (lines) sparameters at VCE = 1.2 V and IC = 10 mA (s11 and s22
in Smith-Chart, s12 and s21 in polar diagram).
norm. equiv. noise resistance Rn/Z0
minimum noise figure Fmin
6
dB
4
3
2
collector current IC
1 mA
10 mA
20 mA
1
0
0
2
4
6
8
10
frequency f
12
14
GHz
Fig. 10: Measured (symbols) and modelled (lines) optimum
generator refection coefficient Γopt
7
6
5
3
18
Fig. 9: Measured (symbols) and modelled (lines) minimum
noise figure
collector current IC
1 mA
10 mA
20 mA
4
0
2
4
6
8
10
frequency f
12
14
GHz
18
Fig. 11: Measured (symbols) and modelled (lines) normalized
equivalent noise resistance rn = Rn/Z0
CONCLUSION
The excellent agreement between measured and modeled data demonstrate the applicability of the presented smallsignal equivalent circuit for s-parameters as well as rf-noise parameters. Also bias dependent measurements are
performed and good match between measured and modeled data is achieved for all cases, s-parameters as well as noiseparameters.
REFERENCES
[1]
HEWLETT-PACKARD: Fundamentals of RF and Microwave Noise Figure Measurements.
Hewlett-Packard, Application Note 57-1
[2]
R. REUTER ET AL.: Investigation and Modeling of Impact Ionization with Regard to the RF- and Noise Behaviour of HFET
IEEE J. of Microwave Theory and Techniques, Vol. 45, No.6, 1997, pp. 977-983
[3]
M. AGETHEN ET AL. : Consistent Small-Signal and RF-Noise Parameter Modelling of Carbon Doped InP/InGaAs HBT
Conference Proc. Of IMS 2001, Phoenix, USA, May 2001
[5]
M. AGETHEN ET AL.: A new Optimization Strategy based on the Theory of Evolution for the RF-modeling of HFET.
Workshop Proceedings. International IEEE Workshop on Experimentally Based FET Device Modelling & Related
Nonlinear Circuit Design, Kassel, Germany, Juli 1997, pp. 4.1-4.5
[6]
M. AGETHEN ET AL.: Theory of Evolution: New Optimization Strategies for the Modeling of HFET-RF-Noise-Parameters
Conference Proceedings, Microwave and Optronics, 9th Exhibition and Conference on High Frequency Engineering,
MIOP-1997, Sindelfingen, Deutschland, pp. 343-347