Impact ionization in InAlAs/InGaAs HFET's

Moolji, Akbar A.; Bahl, S.R.; Alamo, J.A. del

doi:10.1109/55.296227

Cited by 59 publications

(29 citation statements)

References 13 publications

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“…At a given temperature the ionization rate is proportional to the exponential of the inverse of the field in the high field region, as we have verified with the sidegate measurement [17], [30]. Furthermore, we expect that the number of excess holes in the extrinsic source to be directly proportional to the amount of impact ionization.…”

Section: Equivalent Circuit Modelsupporting

confidence: 54%

A new physical model for the kink effect on InAlAs/InGaAs HEMTs

Somerville

Alamo

Hoke³

Proceedings of International Electron Devices Meeting

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Abstract-We present a new model for the the kink effect in InAlAs/InGaAs HEMT's. The model suggests that the kink is due to a threshold voltage shift which arises from a hole pile-up in the extrinsic source and an ensuing charging of the surface and/or the buffer-substrate interface. The model captures the many of the observed behaviors of the kink, including the kink's dependence on bias, time, temperature, illumination, and device structure. Using the model, we have developed a simple equivalent circuit, which reproduced well the kink's dc characteristics, its time evolution in the nanosecond range, and its dependence on illumination.

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Section: Equivalent Circuit Modelsupporting

confidence: 54%

A new physical model for the kink effect on InAlAs/InGaAs HEMTs

Somerville

Alamo

Hoke³

Proceedings of International Electron Devices Meeting

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“…Furthermore, it is widely agreed that in the on-state, reverse gate current arises as a result of impact ionization [8], [18]. Combining these two observations creates a simple picture of the physics of which is consistent with the measurements above and with previous results (Fig.…”

Section: On-state Breakdown Physicssupporting

confidence: 80%

“…Proper calculation of the impact ionization current requires precise knowledge of the fields in the channel and of the ionization rate. It is possible, however, to simplify the problem using the experimentally verified expression [18] (2) can be determined from sidegate measurements; is a scaling constant that depends on device design. While this expression is a phenomenological one, it does capture the key physics of impact ionization: carrier multiplication depends linearly on the electron flux (i.e., ), and has an exponential dependence on the field in the drain-gate gap.…”

Section: On-state Bv Modelmentioning

confidence: 99%

On-state breakdown in power HEMTs: measurements and modeling

Somerville¹,

Blanchard²,

Duh³

et al.

International Electron Devices Meeting. IEDM Technical Digest

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Abstract-We have carried out a systematic study of onstate breakdown in a sample set of InAlAs/InGaAs HEMT's using a new gate current extraction technique in conjunction with sidegate and temperature-dependent measurements. We find that as the device is turned on, the breakdown voltage limiting mechanism changes from a TFE-dominated process to a multiplication-dominated process. This physical understanding allows the creation of a phenomenological physical model for breakdown which agrees well with all our experimental results, and explains the relationship between BVon and the sheet carrier concentration. Our results suggest that depending on device design, either on-state or off-state breakdown can limit maximum power.Index Terms-Breakdown, HEMT, impact ionization, MOD-FET.

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“…The side gate current was extracted by setting a large negative voltage VsG on the side gate, between -20 and -25 V. VSG is selected to maximize the amount of side gate current that is extracted, while minimizing its influence on the I-V characteristics. At first, we checked that ISG is indeed dominated by the impact-ionization generated holes, using the method of [26] and found this to be the case. Fig.…”

Section: Constant Vdgo-constant Idmentioning

confidence: 99%

“…We did this by monitoring the side gate current ISG on mHEMTs with a sidegate structure. This current is well known to be proportional to the impact ionization rate in HFETs [26]. The side gate current was extracted by setting a large negative voltage VsG on the side gate, between -20 and -25 V. VSG is selected to maximize the amount of side gate current that is extracted, while minimizing its influence on the I-V characteristics.…”

Section: Constant Vdgo-constant Idmentioning

confidence: 99%

Electrical degradation of InAlAs/InGaAs metamorphic high-electron mobility transistors

Mertens

Alamo²

International Electron Devices Meeting. Technical Digest (Cat. No.01CH37224)

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InAlAs/InGaAs metamorphic High Electron Mobility Transistors (HEMT) hold promise for power-millimeter wave applications. A major reliability concern in some of these devices is the degradation of the drain resistance that is observed when the device is electrically stressed for a long time at bias conditions necessary for power applications. The goal of this thesis was to find the physical origin of this reliability problem and to suggest solutions to it. State-of-the-art InAlAs/InGaAs metamorphic HEMTs, provided by our sponsor, Hewlett Packard, were stressed under different bias schemes. It was found that most figures of merit associated with the drain-side of the device degrade under severe bias stress. In particular, the drain resistance, RD, has been found to increase significantly. In order to understand the physical origin of this degradation, we have studied the degradation of simpler Transmission Line Model (TLM) structures. We have found that in TLMs and HEMTs there appear to be two different degradation modes, both associated with hot electrons. In the first degradation mechanisms, we postulate that hot electrons are trapped by defects at the interface between the GaAs etch-stopper and the AlInAs Schottky barrier layer, depleting the carrier concentration in the channel underneath. In the second mechanism hot electrons degrade the InGaAs ohmic contacts. No degradation mechanism associated with the metamorphic nature of the structure has been identified. AcknowledgementsI would like to thank Prof. Jesus del Alamo for giving me the chance to work on this interesting project. He has guided me through this research with a huge amount of patience, ideas and red ink, teaching me a methodology in research and reporting. He always tried to make time available for me, even if he was extremely busy. I would like to thank him for offering me the opportunity to be a teaching assistant for his very interesting class and for giving me a place at MIT from the time I arrived. This research has been funded by Hewlett-Packard. I would like to thank Don D'Avanzo for starting this project, appropriating the funding and giving me the opportunity to work as a SEED student in Santa Rosa. Larry Studebaker, thanks for the invaluable help and the samples during the year and the supervision this Summer. I am very happy that I have found such a great co-advisor. I had a great time in Santa Rosa and I learned a lot there, also thanks to Dan Scherrer, Fred Sughiwo and Bob Yeats. HP Labs also helped me a lot through this thesis. Hans Rohdin, thank you for answering so many questions, reading this thesis on time and sending me the samples that helped pull things together. Thanks to Arlene Wakita and Nick Moll for making these devices available to me.Roxann Blanchard, thanks for all the discussions we held and the questions you answered, even when you were busy with your own thesis. You have proven to be an infinite well of knowledge and I can only hope I have been able to soak up enough of it to continue this research.Tassan...

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Impact ionization in InAlAs/InGaAs HFET's

Cited by 59 publications

References 13 publications

A new physical model for the kink effect on InAlAs/InGaAs HEMTs

A new physical model for the kink effect on InAlAs/InGaAs HEMTs

On-state breakdown in power HEMTs: measurements and modeling

Electrical degradation of InAlAs/InGaAs metamorphic high-electron mobility transistors

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