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- Title
Highly Conductive n-Al 0.65 Ga 0.35 N Grown by MOCVD Using Low V/III Ratio.
- Authors
Zollner, Christian J.; Yao, Yifan; Wang, Michael; Wu, Feng; Iza, Michael; Speck, James S.; DenBaars, Steven P.; Nakamura, Shuji
- Abstract
Highly conductive silicon-doped AlGaN and ohmic contacts are needed for deep-UV LEDs and ultrawide bandgap electronics. We demonstrate improved n-Al0.65Ga0.35N films grown by metal–organic chemical vapor deposition (MOCVD) on sapphire substrates using a low V/III ratio (V/III = 10). A reduced V/III ratio improves repeatability and uniformity by allowing a wider range of silicon precursor flow conditions. AlxGa1−xN:Si with x > 0.5 typically has an electron concentration vs. silicon concentration trend that peaks at a particular "knee" value before dropping sharply as [Si] continues to increase (self-compensation). The Al0.65Ga0.35N:Si grown under the lowest V/III conditions in this study does not show the typical knee behavior, and instead, it has a flat electron concentration trend for [Si] > 3 × 1019 cm−3. Resistivities as low as 4 mΩ-cm were achieved, with corresponding electron mobility of 40 cm2/Vs. AFM and TEM confirm that surface morphology and dislocation density are not degraded by these growth conditions. Furthermore, we report vanadium-based ohmic contacts with a resistivity of 7 × 10−5 Ω-cm2 to AlGaN films grown using a low V/III ratio. Lastly, we use these highly conductive silicon-doped layers to demonstrate a 284 nm UV LED with an operating voltage of 7.99 V at 20 A/cm2, with peak EQE and WPE of 3.5% and 2.7%, respectively.
- Subjects
OHMIC contacts; CHEMICAL vapor deposition; ELECTRON mobility; DISLOCATION density; SURFACE morphology; VANADIUM
- Publication
Crystals (2073-4352), 2021, Vol 11, Issue 8, p1006
- ISSN
2073-4352
- Publication type
Article
- DOI
10.3390/cryst11081006