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Interfacial Impurities and Their Electronic Signatures in High-Voltage Regrown Nonpolar m-Plane GaN Vertical p–n Diodes

Physica Status Solidi. A, Applications and Materials Science

Aragon, Andrew; Monavarian, Morteza; Stricklin, Isaac; Pickrell, Gregory W.; Crawford, Mary H.; Allerman, A.A.; Armstrong, Andrew A.; Feezell, Daniel

Impacts of silicon, carbon, and oxygen interfacial impurities on the performance of high-voltage vertical GaN-based p–n diodes are investigated. The results indicate that moderate levels (≈5 × 1017 cm-3) of all interfacial impurities lead to reverse blocking voltages (Vb) greater than 200 V at 1 μA cm-2 and forward leakage of less than 1 µA cm-2 at 1.7 V. At higher interfacial impurity levels, the performance of the diodes becomes compromised. Herein, it is concluded that each impurity has a different effect on the device performance. For example, a high carbon spike at the junction correlates with high off-state leakage current in forward bias (≈100× higher forward leakage current compared with a reference diode), whereas the reverse bias behavior is not severely affected (> 200 V at 1 μA cm-2). High silicon and oxygen spikes at the junction strongly affect the reverse leakage currents (≈ 1–10 V at 1 μA cm-2). Regrown diodes with impurity (silicon, oxygen, and carbon) levels below 5 × 1017 cm-3 show comparable forward and reverse results with the reference continuously grown diodes. The effect of the regrowth interface position relative to the metallurgical junction on the diode performance is also discussed.

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TYPE Journal Article YEAR 2019
DOIOSTI

Investigation of dry-etch-induced defects in >600 v regrown, vertical, GaN, p-n diodes using deep-level optical spectroscopy

Journal of Applied Physics

Pickrell, Gregory W.; Armstrong, Andrew A.; Allerman, A.A.; Crawford, Mary H.; Glaser, Caleb E.; Kempisty, J.; Abate, Vincent M.

The impact of dry-etch-induced defects on the electrical performance of regrown, c-plane, GaN p-n diodes where the p-GaN layer is formed by epitaxial regrowth using metal-organic, chemical-vapor deposition was investigated. Diode leakage increased significantly for etched-and-regrown diodes compared to continuously grown diodes, suggesting a defect-mediated leakage mechanism. Deep level optical spectroscopy (DLOS) techniques were used to identify energy levels and densities of defect states to understand etch-induced damage in regrown devices. DLOS results showed the creation of an emergent, mid-gap defect state at 1.90 eV below the conduction band edge for etched-and-regrown diodes. Reduction in both the reverse leakage and the concentration of the 1.90 eV mid-gap state was achieved using a wet chemical treatment on the etched surface before regrowth, suggesting that the 1.90 eV deep level contributes to increased leakage and premature breakdown but can be mitigated with proper post-etch treatments to achieve >600 V reverse breakdown operation.

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TYPE Journal Article YEAR 2019
DOIOSTIScopus

Saturation Velocity Measurement of Al0.7Ga0.3N-Channel High Electron Mobility Transistors

Journal of Electronic Materials

Klein, Brianna A.; Baca, Albert G.; Lepkowski, Stefan; Nordquist, Christopher D.; Wendt, Joel R.; Allerman, A.A.; Armstrong, Andrew A.; Douglas, Erica A.; Abate, Vincent M.; Kaplar, Robert

Gate length dependent (80 nm–5000 mm) radio frequency measurements to extract saturation velocity are reported for Al0.85Ga0.15N/Al0.7Ga0.3N high electron mobility transistors fabricated into radio frequency devices using electron beam lithography. Direct current characterization revealed the threshold voltage shifting positively with increasing gate length, with devices changing from depletion mode to enhancement mode when the gate length was greater than or equal to 450 nm. Transconductance varied from 10 mS/mm to 25 mS/mm, with the 450 nm device having the highest values. Maximum drain current density was 268 mA/mm at 10 V gate bias. Scattering-parameter characterization revealed a maximum unity gain bandwidth (fT) of 28 GHz, achieved by the 80 nm gate length device. A saturation velocity value of 3.8 × 106 cm/s, or 35% of the maximum saturation velocity reported for GaN, was extracted from the fT measurements.

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TYPE Journal Article YEAR 2019
DOIOSTIScopus

Visible- and solar-blind photodetectors using AlGaN high electron mobility transistors with a nanodot-based floating gate

Photonics Research

Armstrong, Andrew A.; Klein, Brianna A.; Allerman, A.A.; Baca, Albert G.; Crawford, Mary H.; Podkaminer, Jacob; Perez, Carlos; Siegal, Michael P.; Douglas, Erica A.; Abate, Vincent M.; Leonard, Francois

AlGaN-channel high electron mobility transistors (HEMTs) were operated as visible- and solar-blind photodetectors by using GaN nanodots as an optically active floating gate. The effect of the floating gate was large enough to switch an HEMT from the off-state in the dark to an on-state under illumination. This opto-electronic response achieved responsivity > 108 A/W at room temperature while allowing HEMTs to be electrically biased in the offstate for low dark current and low DC power dissipation. The influence of GaN nanodot distance from the HEMT channel on the dynamic range of the photodetector was investigated, along with the responsivity and temporal response of the floating gate HEMT as a function of optical intensity. The absorption threshold was shown to be controlled by the AlN mole fraction of the HEMT channel layer, thus enabling the same device design to be tuned for either visible- or solar-blind detection.

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TYPE Journal Article YEAR 2019
DOIOSTIScopus
Results 76–100 of 363
Results 76–100 of 363