Control Of Emission Wavelength Research Articles

Emission Wavelength Control of Si-rich SiOx MOSLED by Detuning Vapor Fluence and Plasma Power During PECVD Growth

ABSTRACTPhotoluminescence (PL) intensity and wavelength control of Si-rich SiOx film and Si-rich SiOx based MOSLED achieved by detuning plasma power (RF power) during plasma-enhanced chemical vapor deposition (PECVD) growth is investigated. The peak of PL spectrum blue-shifts from 780 to 400 nm by modifying the RF power form 20 to 70 W during PECVD growth. The average sizes of Si nanocluster under RF power of 60 and 70W are 2.61 and 1.83 nm, respectively. The EL color of Si nanocrystal (nc-Si) based MOSLEDs can be tunable among orange-red, green and blue colors by growing the SiOx films with PECVD under different RF power. Under RF power from 50 to 70W, the turn-on voltage of nc-Si based MOSLEDs increases from 26 to 60 V, the optical power also increases from 1.6 W/cm2 to 9.7 W/cm2 and the power-current slope are 0.51, 3.24 and 62.92 mW/A, respectively.

Contactless electroreflectance and photoluminescence of InAs quantum dots with GaInNAs barriers grown on GaAs substrate

AbstractInAs quantum dots (QDs) with GaInNAs barriers grown on (001) GaAs substrate by molecular beam epitaxy have been studied by contactless electroreflectance (CER) and photoluminescence (PL) spectroscopies. It has been observed that the overgrowth of self‐organized InAs QDs with GaInNAs layers effectively tunes the QD emission to the 1.3 μm spectral region. In case of PL spectra only one peak related to QD emission has been observed. In the case of CER spectra, in addition to a CER feature corresponding to the QD ground state, a rich spectrum of CER resonances related to optical transitions in InAs/GaInNAs/GaAs QW has been observed. It has been concluded that the application of GaInNAs instead InGaAs leads to better control of emission wavelength from InAs QDs since strains in GaInNAs can be tuned from compressive to tensile. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Size and emission wavelength control of InAs∕InP quantum wires

For a certain heteroepitaxial system, the optical properties of self-assembled nanostructures basically depend on their size. In this work, we have studied different ways to modify the height of InAs∕InP quantum wires (QWrs) in order to change the photoluminescence emission wavelength. One procedure consists of changing the QWr size by varying the amount of InAs deposited. The other two methods explored rely on the control of As∕P exchange process, in one case during growth of InAs on InP for QWr formation and in the other case during growth of InP on InAs for QWr capping. The combination of the three approaches provides a fine tuning of QWr emission wavelength between 1.2 and 1.9μm at room temperature.

Emission wavelength control of InAs quantum dots in a GaInAsP matrix grown on InP(3 1 1)B substrates

We present the control of the emission wavelength of InAs quantum dots in a GaInAsP matrix grown on InP(3 1 1)B substrates by gas source molecular beam epitaxy. By growing the capping layer in two steps, the control of the dot height and thus of the emission wavelength is achieved. The dot height is tuned using As/P exchange during a growth interrupt. We have studied the changes induced by the nature of the overpressure (As, P, As and P) during the growth interrupt. Photoluminescence spectra at room temperature show the effects of the different growth parameters on the peak energy and width.

Control of Emission Wavelength of GaInN Single Quantum Well, Light Emitting Diodes Grown by Metalorganic Chemical Vapor Deposition in a Split-Flow Reactor

We investigated the dependence of the electroluminescence (EL) characteristics on the layer thickness and the solid-phase composition of AlGaN clad layers in GaInN single-quantum-well light-emitting diodes (LEDs), and how to control the emission wavelength by the device structure. GaInN well layers were sandwiched by AlGaN clad layers, and GaInN inter layers were inserted between GaN n-contact and AlGaN n-clad layers. A wavelength shift of about 50 nm was achieved by changing either the Al solid-phase composition or the thickness of the clad layer. Due to an increase of the lattice mismatch between the clad and the well layers, the emission wavelength increased and the peak intensity decreased. Compared with the performance without an inter layer, the peak intensity increased 3.8 times. Moreover, by changing the growth temperature of the well layer, the LED wavelength can be varied from blue to red. Though the difference of the emission wavelength was 40 nm in the radial direction of the wafer, a luminous intensity of 1 cd for yellowish LEDs was achieved.

Laser diode structure for the generation of high-power picosecond optical pulses

A laser diode structure is designed and tested that permits the generation of high-power (∼100 W) picosecond-range optical pulses. Direct current pumping is used with a current pulse duration of a few nanoseconds and a current amplitude of ∼105 A/cm2. The main distinguishing feature of the structure is separation of the electron injector (p–n junction) from the active region by a potential barrier. The optical gain in the active region is controlled by the transverse electric field, which is determined by the magnitude of the current at each instant. The design allows emission wavelength control by means of band gap engineering.

Emission wavelength control by potential notch in type-II InAs/GaSb/AlSb intersubband light-emitting structures

A potential notch in the well region is used to control the emission wavelength of type-II InAs/GaSb/AlSb intersubband light-emitting structures. Intersubband absorption measurements are performed to evaluate the subband structure of the active layers and are compared with theory. Type-II quantum cascade structures using these active layers are fabricated and midinfrared intersubband electroluminescence is observed. Calculation indicates that the active layer structure can emit electromagnetic waves in the THz region without employing a wide alloy well.

Operation of Tm3+ fiber laser at λ = 2.3 μm coupled to a silica fiber Bragg grating

A wavelength tunable all fibre laser which utilizes Tm3+-doped fluoride fibre as a gain mechanism emitting around a wavelength of λ = 2.3 μm is reported. Tm3+-doped fluoride fibre was coupled to a fibre Bragg grating inscribed in silica. This laser was evaluated by employing it as a wavelength tunable source in a methane gas optical sensor. A minimum gas detectivity of 100 ppm m limited by the ability to prepare low concentrations of gases was achieved. Emission wavelength control was implemented by thermally tuning the grating, although this method may prove to be too slow and cumbersome for practical use. A model describing the coupling between the silica fibre Bragg grating and the Tm3+-doped fibre was developed and integrated with a fibre laser model. This theoretical framework was used to examine the optimum silica and fluoride fibre parameters to achieve the maximum coupling between the fibres, with the aim of further reducing the fibre laser threshold.