Multiquantum-well Diodes Research Articles

Bias-controlled modulation for monolithic III-nitride optoelectronic integration.

III-nitride multi-quantum well (MQW) diodes can modulate the light emitted by another diode with the same MQW structure by varying the bias voltage owing to the spectral overlap between the electroluminescence spectrum and spectral responsivity curve of the MQW diodes. Here, we investigate bias-controlled modulation by monolithically integrating an optical transmitter, waveguide, electro-absorption modulator (EAM), and slot grating coupler on a silicon-based III-nitride platform using compatible fabrication processes. The modulated light is coupled into a fiber, which is direct to a photodiode for characterization. The bandwidths of forward-biased emission modulation and reverse-biased absorption modulation are of the same order of magnitude, with the latter exhibiting significant performance improvements. In addition, real-time video signal transmission was achieved using an EAM, which provides a meaningful reference for modulation applications of silicon-based GaN optoelectronic integrated systems.

Edge-Terminated AlGaN/GaN/AlGaN Multi-Quantum Well Impact Avalanche Transit Time Sources for Terahertz Wave Generation

Edge-Terminated AlGaN/GaN/AlGaN Multi-Quantum Well Impact Avalanche Transit Time Sources for Terahertz Wave Generation

Miniaturized III‐Nitride Asymmetric Optical Link for the Monitoring of Vascular Heart Rate and Cardiac‐Related Pulse Activity

Multifunctioning InGaN/GaN multi‐quantum well (MQW) diodes can transmit and detect light separately. In particular, MQW diodes have spectral overlap between electroluminescence (EL) and responsivity, conferring the unique ability to detect light emitted by another device sharing an identical MQW structure. Herein, a III‐nitride transmitter and a receiver on a single chip are monolithically integrated, which can establish an asymmetric optical link and significantly reduce material and processing costs. By attaching the chip to the skin with the transmitter emitting toward it, the device can monitor cardiac activity. Heart pulses change blood volume of the vascular bed, which modulates the reflected light. The receiver absorbs that light and converts it into electrical signals. Finally, by integrating a programmed circuit, the biological signals are analyzed. Herein, a feasible approach to monitor heart rate and cardiac‐related pulse information simultaneously is provided.

Room temperature InPSb/InAs and InPSb/InAs/InAsSb mid-infrared emitting diodes grown by MOVPE

Strained InAsSb heterostructures are important materials for a variety of new III-V based mid-infrared emitters. In the study InP/sub 0.69/-Sb/sub 0.31/-InAs light-emitting diodes (LEDs) employing an InAs-InAs/sub 0.94/Sb/sub 0.06/ multiquantum-well (MQW) active region have been investigated. They were characterised using electro-optical techniques and X-ray diffractometry. The authors have measured the temperature dependence of electroluminescence (EL): at low temperatures, the EL-intensity of the MQW diodes is higher than that of a simple PIN InPSb-InAs-InPSb structure. For both devices, room temperature EL could be resolved (emission wavelength of 3.3 /spl mu/m, FWHM of 70 meV) which is related to InAs near-bandgap transitions. InAsP/InAsSb MQWs were grown to achieve higher antimony contents in the wells. The heterostructures were strain-balanced and enabled an antimony incorporation of 24% with, at the same time, high structural quality. In the photoluminescence (PL) spectra of InAs/sub 0.95/P/sub 0.05/-InAs/sub 0.86/Sb/sub 0.14/ MQWs strong features were observed around 4.2 /spl mu/m due to atmospheric CO/sub 2/ absorption.

Optical bistability of In 0.52 Al 0.48 As/InPtype II multi-quantum well diodes

Optical bistability was observed in the current-light output (I-L) characteristic of an InAlAs/InP type II multi-quantum well (MQW) diode for the first time. With bistability, light output suddenly increases at 70 mA when the current increases; it suddenly decreases at 30 mA when the current decreases. We found that the bistability of the I-L characteristic corresponds exactly to the bistability of the current-voltage (I-V) characteristic of the InAlAs/InP MQW diode.

Dependence of device characteristics on quantum well thickness in ZnSe/ZnCdSe multi-quantum well blue-green laser diodes

ZnSe/Zn 0.85Cd 0.15Se multi-quantum well (MQW) diode structures with different well thicknesses ( L w) in the range of 6–13 nm were fabricated, and device characteristics of the diodes were studied in terms of crystalline quality of the MQW layers. In order to investigate the relationship between the device characteristics and the crystalline quality of the MQW layers, the intensity of spontaneous emission from MQW diode structures was measured. The emission intensity increased with increasing L w and showed a maximum value at L w = 10 nm, followed by rather rapid reduction of the emission intensity at L w > 10 nm. This decrease of emission intensity is suggested to be due to the lattice relaxation caused by dislocation formation at the interface taking account of critical thickness of the MQW structure. The lasing characteristics of ZnSe/ZnCdSe MQW blue-green laser diodes are also described.

Effect of an electric field on electron and hole wave functions in a multiquantum well structure

Electron and hole energy levels and eigenstates, and the overlap of electron and hole wave functions are calculated for four-well multiquantum well (MQW) structures assuming a uniform electric field with Airy function solutions. MQW are found to be much more sensitive to electric fields than single wells. Stark ladder formation is observed in the valence-band wells at low fields, and in the conduction band at high fields. It is found that the Δm=0 mode selection rule is violated by fields smaller than those thought to exist in MQW diode lasers.