Joel De Jesus

High performance, room temperature, broadband II-VI quantum cascade detector

We report on the experimental demonstration of a room temperature, II-VI, ZnCdSe/ZnCdMgSe, broadband Quantum Cascade detector. The detector consists of 30 periods of 2 interleaved active-absorption regions centered at wavelengths 4.8 μm and 5.8 μm, respectively. A broad and smooth photocurrent spectrum between 3.3 μm and 6 μm spanning a width of 1030 cm–1 measured at 10% above baseline was obtained up to 280 K, corresponding to a ΔE/E of 47%. Calibrated blackbody responsivity measurements show a measured peak responsivity of 40 mA/W at 80 K, corresponding to a detectivity of about 3.1×1010 cmHz/W. Bias dependent photocurrent measurements revealed no significant change in the spectral shape, suggesting an impedance matched structure between the different active regions.

High detectivity short-wavelength II-VI quantum cascade detector

We demonstrate the first II-VI based short-wave (λ ≤ 4 μm) Quantum Cascade Detector. Peak responsivity and background limited detectivity of 0.1 mA/W and 2.5×10¹⁰ cm√Hz/W, respectively, were measured at 80 K.

Hybrid GaN LED with capillary-bonded II–VI MQW color-converting membrane for visible light communications

The rapid emergence of gallium-nitride (GaN) light-emitting diodes (LEDs) for solid-state lighting has created a timely opportunity for optical communications using visible light. One important challenge to address this opportunity is to extend the wavelength coverage of GaN LEDs without compromising their modulation properties. Here, a hybrid source for emission at 540 nm consisting of a 450 nm GaN micro-sized LED (micro-LED) with a micron-thick ZnCdSe/ZnCdMgSe multi-quantum-well color-converting membrane is reported. The membrane is liquid-capillary-bonded directly onto the sapphire window of the micro-LED for full hybridization. At an injection current of 100 mA, the color-converted power was found to be 37 μW. At this same current, the −3 dB optical modulation bandwidth of the bare GaN and hybrid micro-LEDs were 79 and 51 MHz, respectively. The intrinsic bandwidth of the color-converting membrane was found to be power-density independent over the range of the micro-LED operation at 145 MHz, which corresponds to a mean carrier lifetime of 1.9 ns.

Molecular Beam Epitaxial Growth and Properties of Bi2Se3 Topological Insulator Layers on Different Substrate Surfaces

Growth of high-quality Bi2Se3 films is crucial not only for study of topological insulators but also for manufacture of technologically important materials. We report a study of the heteroepitaxy of single-crystal Bi2Se3 thin films grown on GaAs and InP substrates by use of molecular beam epitaxy. Surface topography, crystal structure, and electrical transport properties of these Bi2Se3 epitaxial films are indicative of highly c-axis oriented films with atomically sharp interfaces.

MBE growth of ZnCdSe/ZnCdMgSe quantum-well infrared photodetectors

The authors report the growth of quantum well infrared photodetectors (QWIPs) made from wide band gap II-VI semiconductors. ZnCdSe/ZnCdMgSe QWIPs in both medium-wave infrared and long-wave infrared regions were grown by molecular beam epitaxy on InP substrates. High-resolution x-ray diffraction and photoluminescence measurements showed that the as-grown samples have high structural and optical quality. Spectral responses with peaks at 8.7 μm and 4.0 μm have been obtained.

MgSe/ZnSe/CdSe coupled quantum wells grown on InP substrate with intersubband absorption covering 1.55 μm

The authors report the observation of intersubband (ISB) transitions in the optical communication wavelength region in MgSe/ZnSe/CdSe coupled quantum wells (QWs). The coupled QWs were grown on InP substrates by molecular beam epitaxy. By inserting ZnSe layers to compensate the strain, samples with high structural quality were obtained, as indicated by well resolved satellite peaks in high-resolution x-ray diffraction. The observed ISB transition energies agree well with the calculated values.

Improved electrical properties and crystalline quality of II–VI heterostructures for quantum cascade lasers

The authors report on investigations of the doping, lattice mismatch, and interface quality for the molecular beam epitaxial growth of ZnCdSe/ZnCdMgSe/InP quantum cascade structures with improved electrical, structural, and spectral properties. An improved doping strategy, the control of the lattice mismatch to less than 0.25%, and the incorporation of growth interruptions have led to quantum cascade structures with good I–V characteristics and electroluminescence emission up to room temperature, with an emission energy of 230 meV (5.4 μm) and a full-width at half maximum of 41 meV at 80 K, the best device properties reported so far for this material system. It is expected that the addition of waveguide layers in the structure will lead to the observation of lasing.

Characterization of the three-well active region of a quantum cascade laser using contactless electroreflectance

Quantum cascade (QC) lasers with emission at wavelengths below 4 μm are difficult to achieve from conventional III-V materials systems lattice matched to GaAs and InP due to the limited conduction band offset (CBO) of those materials that results from the presence of intervalley scattering. The II-VI materials ZnCdSe/ZnCdMgSe, with a CBO as high as 1.12 eV and no intervalley scattering, are promising candidates to achieve this goal. Using molecular beam epitaxy (MBE), the authors grew a QC laser structure with a three-well active region design made of ZnCdSe and ZnCdMgSe multilayers closely lattice matched to InP. A test structure, which contains only the active region of the QC laser separated by quaternary barrier layers, was also grown. The test structure was characterized by contactless electroreflectance (CER). Photoluminescence measurements and a model based on the transfer matrix method were used to identify the CER transitions. The energy levels obtained for the test structure were then used to pr...

Long wave, room temperature II-VI-based quantum cascade emitters

We demonstrate the first long-wave, room temperature II-VI materials based Quantum Cascade emitter around 7.2 μm. At 80 K, a device differential resistance of 2.6 Ω and a narrow electroluminescent width of 16% was obtained.