Sixuan Jin

InGaN/GaN quantum well interconnected microdisk light emitting diodes

Interconnected microdisk light-emitting diodes (μ-LEDs) have been fabricated from InGaN/GaN single quantum wells grown by low pressure metal organic chemical vapor deposition. These interconnected μ-disk LEDs fit into the same device area taken up by a conventional broad-area LED. The performance characteristic of these interconnected μ-disk LEDs, including I–V and L–I characteristics as well as electroluminescence spectra have been measured and compared with those of the conventional broad-area LEDs. For interconnected μ-disk LEDs, while VF, the forward biased voltage at 20 mA, was slightly increased, the emission efficiency was increased by as much as 60% over the conventional LEDs for a fixed device area. The results thus suggested that replacing a conventional broad-area LED with an interconnected μ-disk LED, the external quantum efficiency can be significantly enhanced. Finally, the fabrication processes of the interconnected μ-disk LEDs are almost the same as those of the conventional broad-area LED...

GaN microdisk light emitting diodes

Microdisk light-emitting diodes (μ-LEDs) with diameter of about 12 μm have been fabricated from InGaN/GaN quantum wells. Photolithographic patterning and inductively coupled plasma dry etching have been employed to fabricate these μ-LED devices. Device characteristics, such as the current–voltage characteristics, light output power, and electroluminescence (EL) spectra have been measured and compared with those of conventional broad-area LEDs. Our results showed that, for an identical area, the quantum efficiencies of μ-LED are enhanced over the conventional broad-area LEDs due to an enhanced current density and possibly microsize effects. The implications of our results on the design of future UV/blue microoptoelectronic devices are discussed.

Electroluminescent properties of erbium-doped III–N light-emitting diodes

We report on the synthesis of Er-doped III–N double heterostructure light-emitting diodes (LEDs) and their electroluminescence (EL) properties. The device structures were grown through a combination of metalorganic chemical vapor deposition (MOCVD) and molecular-beam epitaxy (MBE) on c-plane sapphire substrates. The AlGaN layers, with an Al concentration of ∼12%, were prepared by MOCVD and doped with Si or Mg to achieve n- and p-type conductivity, respectively. The Er+O-doped GaN active region was grown by MBE and had a thickness of 50 nm. The Er concentration was estimated to be ∼1018 cm−3. The multilayer n-AlGaN/GaN:Er/p-AlGaN structures were processed into LEDs using standard etching and contacting methods. Several different LEDs were produced and EL spectra were recorded with both forward and reverse bias conditions. Typically, the EL under reverse bias was five to ten times more intense than that under forward bias. The LEDs displayed a number of narrow emission lines representative of the GaN:Er sys...

Birefringence of GaN/AlGaN optical waveguides

We have experimentally studied the birefringence of wurtzite GaN grown on a sapphire substrate. The measurements were done with single-mode GaN/AlGaN planar optical waveguides on c-plane grown heterostructure films. The refractive indices were found to be different for signal optical field perpendicular or parallel to the crystal c axis (n⊥≠n∥). More importantly, we found an approximately 10% change in index difference Δn=n∥−n⊥ with variation of the waveguide orientation in the a–b plane, and a 60° periodicity was clearly observed. This is attributed to the hexagonal structure of nitride materials.

SiO2/TiO2 distributed Bragg reflector near 1.5 μm fabricated by e-beam evaporation

The authors report on the fabrication and characterization of SiO2/TiO2 distributed Bragg reflector (DBR) mirrors operating at the eye safe and optical communication wavelength window, λ = 1.5 μm. Our experimental results demonstrated that SiO2/TiO2 DBR mirrors with reflectivity exceeding 95% at λ = 1.5 μm can be achieved using e-beam evaporation in conjunction with postdeposition thermal annealing process in ambient air. It was found that the postdeposition annealing process transformed the crystal structure of the as-deposited TixOy to TiO2, leading to a significant reduction in optical absorption. Erbium doped III-nitride semiconductors incorporating DBR mirrors at 1.5 μm emission may open up many novel applications, including infrared emitters, optical amplifiers, and high power infrared lasers.

III-nitride-based planar lightwave circuits for optical communications

Planar lightwave circuits based on III-nitride wide-bandgap semiconductors is proposed and demonstrated for the first time. The feasibility of developing III-nitride-based photonic integrated circuits for applications in 1550 nm fiber-optic communications is discussed.