Thermal influence on S₂₂ kink behavior of a 0.15 μm gate length AlGaN/GaN/SiC HEMT for microwave applications

Abstract

Thermal influence on S 22 kink behavior has been carried out on a 0.15 μm gate length AlGaN/ GaN/SiC high electron mobility transistor over a wide range of temperature. The size and the shape of the S 22 kink effect (KE) in terms of biasing and temperature have been evaluated. The main finding is that S 22 of the studied device is affected by two kinks: the first one appears at approximately 19 GHz and then the second one appears at about 43 GHz. The impact of the intrinsic circuit parameters on the S 22 kink phenomena is inspected to assess their contribution. In addition, a new procedure is proposed to quantify this type of phenomenon by defining the kink area as the area between the two curves corresponding to S 22 with and without the KE. The relevance of this study emerges from the fact that an exhaustive characterization of these anomalous phenomena can empower RF engineers to effectively take them into account for both modeling and design purposes.

Multibias and temperature dependence of the current‐gain peak in GaN HEMT

“…Here, a method is proposed to measure the area of the current‐gain peak (ACGP) as the zone between the two graphs comparing h 21 with and without the peak. This is an extension of our earlier work in which we applied such a methodology to quantify the size of the kink effect in the output reflection coefficient ( S 22 ) . The kink effect in S 22 consists of a change of the output impedance ( Z out ) from a low‐frequency series RC circuit to a high‐frequency parallel RC circuit …”

“…The drain bias V ds was varied from 0 to 15 V and the gate bias V gs was varied from −3 to −6 V. The measurements were performed using a thermal probe station integrated with an HP8510C vector network analyzer with the help of commercial software to ensure the data free from human error. Figure illustrates the standard small‐signal equivalent circuit used to model the tested device …”

“…Figure 1 illustrates the standard small-signal equivalent circuit used to model the tested device. 12 The short-circuit current-gain is denoted as the hybrid parameter h 21 which can be determined by the impedance (Z-) parameters as 4 :…”

“…This is an extension of our earlier work in which we applied such a methodology to quantify the size of the kink effect in the output reflection coefficient (S 22 ). 12 The kink effect in S 22 consists of a change of the output impedance (Z out ) from a low-frequency series RC circuit to a high-frequency parallel RC circuit. 6,[12][13][14][15][16][17][18] This article explores the multibias, frequency, and temperature dependence of the behavior of h 21 and its relative parameter Z 22 for a GaN-based HEMT.…”

“…12 The kink effect in S 22 consists of a change of the output impedance (Z out ) from a low-frequency series RC circuit to a high-frequency parallel RC circuit. 6,[12][13][14][15][16][17][18] This article explores the multibias, frequency, and temperature dependence of the behavior of h 21 and its relative parameter Z 22 for a GaN-based HEMT. The detection of the peak in h 21 and the dip in Z 22 has been accomplished by means of on-wafer scattering (S-) parameter measurements from low (−40 C) to high (150 C) temperature over multibias operation conditions up to 50 GHz.…”