Accurate extrinsic resistances extraction for modeling InP HEMT devices is a crucial step in the design and production of high-yield,low-cost millimeter wave circuits[
Journal of Infrared and Millimeter Waves, Volume. 43, Issue 1, 85(2024)
An improved method for determination of extrinsic resistances for HEMT devices based on 110 GHz S-parameters on-wafer measurement
An improved method for determination of extrinsic resistances for 70 nm InP high electron mobility transistor (HEMT) is proposed in this paper. A set of expressions have been derived from the equivalent circuit model under operating bias points (Vgs > Vth, Vds = 0 V). The extrinsic resistances are iterative determined using the discrepancy between simulated and measured S-parameters as an optimization criterion using the semi-analytical method. Good agreement between simulated and measured S-parameters under multi bias over the frequency range up to 110 GHz verifies the effectiveness of this extraction method.
Introduction
Accurate extrinsic resistances extraction for modeling InP HEMT devices is a crucial step in the design and production of high-yield,low-cost millimeter wave circuits[
In order to overcome these limitations,an improved method for determination of extrinsic resistances is proposed. In contrast with previous publications,this extraction method offers the following advantages.
1)Under operating bias point(Vgs > Vth,Vds = 0 V),the effect of channel between source and drain can be modeled by resistance Rch,while the capacitance will be dominant under cutoff bias condition.
2)The semi-analytical method which is a combination of optimization method and analytical direct extraction method has been used to determine the extrinsic resistances.
3)This extraction method is verified with S-parameters on-wafer measurement up to 110 GHz.
Section Ⅱ gives the equivalent circuit model under operating bias point(Vgs > Vth,Vds = 0 V)as well as the derivation of analytical expressions. Section Ⅲ gives the procedure of intrinsic parameters extraction. The measured and simulated results are presented in Section Ⅳ. The conclusion is given in Section Ⅴ.
1 Extrinsic resistances extraction
1.1 Equivalent circuit model
Figure 1.The small-signal equivalent circuit model under operating bias point(Vgs > Vth,Vds = 0 V)
The intrinsic part of the equivalent circuit model,which exhibits a PI topology,so it is convenient to describe it by a Y matrix as:
Convert
The Z-parameters of intrinsic part with extrinsic resistances can be expressed as following:
Therefore,we have
By neglecting the high order term
where
Cgsa and Cgda can be determined at low frequencies:
1.2 Extrinsic parameters extraction
The pad capacitances can be determined by measuring an open test structure:
The extrinsic inductances Lg,Ld,and Ls can be determined from the imaginary part of Z-parameters(transformed from measured S-parameters)of the short test structure directly:
The extraction of extrinsic resistances can be based on the semi-analytical method which is a combination of optimization method and analytical direct extraction method. The extraction procedure is as follows.
1)De-embedding the pad capacitances and feedline inductances.
2)Set the initial value of the channel resistance Rch .
3)Calculate the extrinsic resistances Rg,Rd,and Rs using(13)-(15)which can be expressed as functions of Rch as well as frequency.
4)Set error criteria as follows:
Where
5)If error criteria are small enough,the iterative process will be end.
Figure 2.Flow chart of the algorithm
2 Intrinsic parameters extraction
The small-signal circuit model of intrinsic part of InP HEMT devices is illustrated in
Figure 3.The small-signal circuit model of intrinsic part
with
From the analytical expressions(27)-(30),the intrinsic element values can be obtained directly.
3 Results and discussion
In this paper,70 nm InP HEMT devices have been used with 2×30 μm gate width(number of gate fingers×unit gate width). The S-paremeters on-wafer measurement up to 110 GHz using N5247 network analyzer with DC bias by an Agilent B1500A.
Figure 4.Extracted extrinsic resistances using the proposed semi-analytical method and cutoff method
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The intrinsic elements listed in
Figure 5.Comparison between simulated (lines) and measured (squares) S-parameters over the frequency range going:from 1 GHz to 110 GHz under multi bias
4 Conclusion
An approach for determination of extrinsic resistances for 70 nm InP HEMT devices is proposed in this paper. Extrinsic resistances are described as functions of the intrinsic channel resistance,and optimum values can be obtained using semi-analytical method under operating bias point(Vgs > Vth,Vds = 0 V). Verification of this extraction method is presented by the good agreement between the simulated and measured S-parameters under multi bias over the frequency range up to 110 GHz.
[6] M Y Jeon, B G Kim, Y J Jeon. A Technique for Extracting Small-Signal Equivalent-Circuit Elements of HEMTs. IEICE Transactions on Electronics, 82, 1968-1976(1999).
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Zhi-Chun LI, Yuan-Ting LYU, Ao ZHANG, Jian-Jun GAO. An improved method for determination of extrinsic resistances for HEMT devices based on 110 GHz S-parameters on-wafer measurement[J]. Journal of Infrared and Millimeter Waves, 2024, 43(1): 85
Category: Research Articles
Received: Mar. 31, 2023
Accepted: --
Published Online: Dec. 26, 2023
The Author Email: GAO Jian-Jun (jjgao@ee.ecnu.edu.cn)