This article reports a nonpolar GaN metal−semiconductor− metal (MSM) photodetector (PD) with an ultrahigh responsivity and an ultrafast response speed in the ultraviolet spectral region, which was fabricated on nonpolar (112̅ 0) GaN stripe arrays with a major improvement in crystal quality grown on patterned (110) silicon substrates by means of using our twostep processes. Our nonpolar GaN MSM-PD exhibits a responsivity of 695.3 A/W at 1 V bias and 12628.3 A/W at 5 V bias, both under 360 nm ultraviolet illumination, which are more than 20 times higher and 4 orders of magnitude higher compared to the current state-of-the-art photodetector, respectively. The nonpolar GaN MSM-PD displays a rise time and a fall time of 66 and 43 μs, respectively, which are 3 orders of magnitude faster compared to the current state-of-the-art photodetector.
This study investigates the applicability of distortion models for predicting dynamic characteristics of a rotating thin-wall short cylindrical shell. The significance of this study is that it provides a necessary scaling law, applicable structure size intervals, and its boundary functions, which can guide the design of distortion models. Sensitivity analysis and governing equations are employed to establish the scaling law between the model and the prototype. Then a commonly used 7050 aluminum alloy cylindrical shell is analyzed as a prototype. The determination of applicable structure size intervals is discussed, and the boundary functions of the applicable structure size intervals are investigated. The applicability of the scaling law and the applicable intervals of rotating thin-wall short cylindrical shell are verified numerically. The results indicate that distortion models that satisfy the structure size applicable intervals can predict the characteristics of the prototype with good accuracy.
To fully exploit
the advantages of GaN for electronic devices,
a critical electric field that approaches its theoretical value (3
MV/cm) is desirable but has not yet been achieved. It is necessary
to explore a new approach toward the intrinsic limits of GaN electronics
from the perspective of epitaxial growth. By using a novel two-dimensional
growth mode benefiting from our high-temperature AlN buffer technology,
which is different from the classic two-step growth approach, our
high-electron-mobility transistors (HEMTs) demonstrate an extremely
high breakdown field of 2.5 MV/cm approaching the theoretical limit
of GaN and an extremely low off-state buffer leakage of 1 nA/mm at
a bias of up to 1000 V. Furthermore, our HEMTs also exhibit an excellent
figure-of-merit (V
br
2/R
on,sp) of 5.13 × 108 V2/Ω·cm2.
High‐quality semi‐polar (11‐22) GaN is obtained by means of growth on patterned (113) silicon substrates featured with stripy grooves and extra periodic gaps which are perpendicular to the grooves. Ga melting‐back during the GaN growth at a high temperature is eliminated as a result of special patterning design. On‐axis X‐ray rocking curve measurements show that the linewidth is significantly reduced down to 339 arcsec. Photoluminescence (PL) measurements at 10 K show strong GaN band‐edge emission only, meaning that any basal stacking fault‐related emission is not observed. Furthermore, green InGaN/GaN light‐emitting diodes (LEDs) with an emission wavelength of around 530 nm are achieved on the semi‐polar GaN grown on the patterned Si substrates. Excitation power‐dependent PL measurements do not show a shift in wavelength, meaning a significant reduction in polarization‐induced piezoelectric fields. Electroluminescence (EL) measurements exhibit that the output power of the semi‐polar LED increases linearly with increasing injection current. It is worth highlighting that the overgrowth technology on designed patterned (113) silicon is a potential approach to manufacturing high‐performance semi‐polar GaN emitters on Si substrates in a long wavelength region.
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