TEM Observation of Crack- and Pit-Shaped Defects in Electrically Degraded GaN HEMTs

Chowdhury, U.; Jiménez, José; Lee, C.; Saunier, P.; Balistreri, Tony; Park, Seong-Yong; Lee, Taehun; Wang, J.; Kim, M.J.; Joh, Jungwoo; Alamo, J.A. del

doi:10.1109/led.2008.2003073

Cited by 146 publications

(124 citation statements)

References 7 publications

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“…This is the first such observation under ON-state stress and is similar to what has been observed in GaN HEMTs under OFF-state stress. 19,20,26 Besides the damage formed at the gate edge, there is an unusual finding of our structural studies in all stressed devices. Both SEM and AFM analyses reveal visible erosion under the entire gate of the device.…”

mentioning

confidence: 58%

“…The damage extends through the GaN cap and the AlGaN barrier layer and in some extreme cases reaches into the GaN buffer layer. 26 It has also been found that the damage is accelerated with stress voltage and temperature and correlates with the drain current degradation suffered by the device. 19,20,[26][27][28] In power amplifier applications, the device is typically biased in the ON state.…”

Section: Introductionmentioning

confidence: 98%

“…26 It has also been found that the damage is accelerated with stress voltage and temperature and correlates with the drain current degradation suffered by the device. 19,20,[26][27][28] In power amplifier applications, the device is typically biased in the ON state. In spite of its importance, there has been very little research on the impact of prolonged highpower stress on the structural degradation of the device.…”

Section: Introductionmentioning

confidence: 98%

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Electrical and structural degradation of GaN high electron mobility transistors under high-power and high-temperature Direct Current stress

Chen

Alamo

2015

Journal of Applied Physics

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We have stressed AlGaN/GaN HEMTs (High Electron Mobility Transistors) under high-power and high-temperature DC conditions that resulted in various levels of device degradation. Following electrical stress, we conducted a well-established three-step wet etching process to remove passivation, gate and ohmic contacts so that the device surface can be examined by SEM and AFM. We have found prominent pits and trenches that have formed under the gate edge on the drain side of the device. The width and depth of the pits under the gate edge correlate with the degree of drain current degradation. In addition, we also found visible erosion under the full extent of the gate. The depth of the eroded region averaged along the gate width under the gate correlated with channel resistance degradation. Both electrical and structural analysis results indicate that device degradation under high-power DC conditions is of a similar nature as in better understood high-voltage OFF-state conditions. The recognition of a unified degradation mechanism provides impetus to the development of a degradation model with lifetime predictive capabilities for a broad range of operating conditions spanning from OFF-state to ON-state.

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mentioning

confidence: 58%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

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Electrical and structural degradation of GaN high electron mobility transistors under high-power and high-temperature Direct Current stress

Chen

Alamo

2015

Journal of Applied Physics

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“…In order to increase the lifetime of AlGaN/GaN HEMTs, it is essential to have a detailed understanding of the mechanisms underlying the degradation of these devices. It has previously been reported that the gate leakage current, I g , degrades when the devices are operated in pinched off conditions or when the gate Schottky contact is reverse biased 2,3,4,5,6,7,8,9,10,11,12 . Some reports have correlated the increase in I g during offstate stress of the devices with the appearance of grooves and v-shaped pits on the surface of the semiconductor, located at the edges of the gate contact 6,7,9,12 .…”

mentioning

confidence: 99%

On the link between electroluminescence, gate current leakage, and surface defects in AlGaN/GaN high electron mobility transistors upon off-state stress

Bajo

Hodges

Uren

et al. 2012

Applied Physics Letters

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The degradation of AlGaN/GaN high electron mobility transistors after off-state stress is studied by means of electroluminescence (EL) analysis, gate leakage current (Ig) monitoring, and atomic force microscopy (AFM) mapping of the semiconductor surface. It is found that the degradation of Ig upon stress is due to the combined effect of the individual defects underlying each of the EL spots, which contribute a few μA each to the total Ig. After removal of contacts and passivation, a direct one-to-one correspondence between EL spots and pits on the semiconductor surface is found. Reverse bias, conducting-tip AFM imaging showed that these surface pits do indeed act as leakage paths. Thus, the direct relationship between EL hot spots, surface pits, and gate current leakage is demonstrated. Discussion on the morphology of the surface pits and their possible origin is also provided.

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“…1(b). The 2DEG has an electron mobility of 1950 cm2/Vs at room temperature, an electron sheet density of 1.5×10 13 cm -2 and an Ohmic contact resistance of 0.3 Ω.mm. The I-V characteristics are measured at DC and dark conditions using Agilent B1500A framework.…”

Section: Introductionmentioning

confidence: 99%

Self-heating and polarization effects in AlGaN/AlN/GaN/AlGaN based devices

Ahmeda

Ubochi

Kálna

et al. 2017

2017 12th European Microwave Integrated Circuits Conference (EuMIC)

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Abstract-The interplay of self-heating and polarization affecting the current is studied in Al0.32Ga0.68N/AlN/GaN/Al0.1Ga0.9N Transmission Line Model (TLM) heterostructures with a scaled source-drain distance. The study is based on meticulously calibrated TCAD simulations against I-V experimental characteristics using an electro-thermal model. The electro-thermal simulations show hot-spots at the edge of the drain contact due to a large electric field affecting the device reliability. Due to the applied electrical stress, the total polarization, relative to the 18 μm heterostructure, decreases by 7 %, 10 % and 17% during a reduction of the source-to-drain distance to the 12 μm, 8 μm, and 4 μm, respectively, as a result of the additional strain induced by electrical stress. This additional stress on source/drain contacts reduces the polarization at the surface as a result of the inverse piezoelectric effect.

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TEM Observation of Crack- and Pit-Shaped Defects in Electrically Degraded GaN HEMTs

Cited by 146 publications

References 7 publications

Electrical and structural degradation of GaN high electron mobility transistors under high-power and high-temperature Direct Current stress

Electrical and structural degradation of GaN high electron mobility transistors under high-power and high-temperature Direct Current stress

On the link between electroluminescence, gate current leakage, and surface defects in AlGaN/GaN high electron mobility transistors upon off-state stress

Self-heating and polarization effects in AlGaN/AlN/GaN/AlGaN based devices

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