Visible‐color‐tunable light‐emitting diodes (LEDs) with electroluminescent color that changes continuously from red to blue by adjusting the external electric bias are fabricated using multifacetted GaN nanorods with anisotropically formed 3D InGaN multiple‐quantum wells. Monolithically integrated red, green, and blue LEDs on a single substrate, operating at a fixed drive current, are also demonstrated for inorganic full‐color LED display applications.

With the motivation of realizing an all graphene-based circuit for low power, we present a reliable nonvolatile graphene memory device, single-layer graphene (SLG) ferroelectric field-effect transistor (FFET). We demonstrate that exfoliated single-layer graphene can be optically visible on a ferroelectric lead-zirconate-titanate (PZT) substrate and observe a large memory window that is nearly equivalent to the hysteresis of the PZT at low operating voltages in a graphene FFET. In comparison to exfoliated graphene, FFETs fabricated with chemical vapor deposited (CVD) graphene exhibit enhanced stability through a bi-stable current state operation with long retention time. In addition, we suggest that the trapping/de-trapping of charge carriers in the interface states is responsible for the anti-hysteresis behavior in graphene FFET on PZT.

4H–SiC samples doped with nitrogen at ∼3×1019 cm−3 were annealed in Ar for 90 min at 1150 °C. Transmission electron microscopy revealed stacking faults at a density of approximately 80 μm−1 where faults were not found to exist prior to annealing. All faults examined were double layer Shockley faults formed by shear on two neighboring basal planes. The structural transformation was interpreted as due to quantum well action, a mechanism where electrons in highly n-type 4H–SiC enter stacking fault-induced quantum well states to lower the system energy. The net energy gain was calculated as a function of temperature and nitrogen doping concentration through solution of the charge neutrality equation. Calculations showed that doping levels in excess of ∼3×1019 cm−3 should result in double layer stacking faults forming spontaneously at device processing temperatures, in agreement with our observations. Single layer faults are not expected to be stable in 4H–SiC at concentrations below 1×1020 cm−3, but are expected to form at doping concentrations above ∼2×1019 cm−3 in 6H–SiC. Charge buildup in the stacking fault was shown to produce an electrostatic potential that exceeds 90% of the energy difference between the Fermi level position and lowest energy state in the fault-related quantum well. This potential barrier is one of the factors leading to increase of the forward voltage drop in SiC pin diodes.

Blue light-emitting diodes ͑LEDs͒ with polarization-matched GaInN/GaInN multi-quantum-well ͑MQW͒ active regions are grown by metal-organic vapor-phase epitaxy. The GaInN/GaInN MQW structure reduces the magnitude of polarization sheet charges at heterointerfaces in the active region. The GaInN/GaInN MQW LEDs are shown to have enhanced light-output power, reduced efficiency droop, a lower forward voltage, a smaller diode ideality factor, and decreased wavelength shift, compared with conventional GaInN/GaN MQW LEDs.

Spontaneous formation of stacking faults in heavily nitrogen-doped 4H-polytype silicon carbide crystals have been observed by transmission electron microscopy (TEM). Faults were present in as-grown boules and additional faults were generated by annealing in argon at 1150 °C. All faults had identical structure consisting of six layers stacked in a cubic sequence as determined by high-resolution TEM, and were interpreted as a result of two Shockley partial dislocations gliding on two neighboring basal planes of SiC. It is argued that the energy of faulted 4H silicon carbide is lower than the energy of perfect heavily doped (n>1×1019 cm−3) crystal at typical processing temperatures, thus providing a driving force for transformation.