Multiple Quantum-well Diodes Research Articles

On-chip warped three-dimensional InGaN/GaN quantum well diode with transceiver coexistence characters

Featured with light emission and detection coexistence phenomenon, nitride-based multiple-quantum-well (MQW) diodes integrated chip has been proven to be an attractive structure for application prospects in various fields such as lighting, sensing, optical communication, and other fields. However, most of the recent reports are based on planar structures. Three-dimensional (3D) structures offer extra advantages in direction and polarization and absorption modulation and may start a new way to make the same thing over and over with interesting properties. In this paper, we designed and fabricated a single-cantilever InGaN/GaN MQW diode with warped 3D microstructure via standard microfabrication technology. Experimental results indicate that the strain architecture of the multi-layer materials is the key principle for the self-warped device. The planar structure will bear greater compressive stress while the warped beam part has less stress, resulting in differences in the optical and electrical performance. The strain-induced band bending highly influences the emission and detection properties, while the warped structure will introduce direction selectivity to the 3D device. As an emitter, 3D structures have a directional emission with lower turn-on voltage, higher capacitance, increased luminous intensity, higher external quantum efficiency (EQE), high -3dB bandwidth, and redshifted peak wavelength. Besides, it can serve as an emitter for directional-related optical communication. As a receiver, 3D structures have lower dark-current, higher photocurrent, and red-shifted response spectrum and also show directional dependence. These findings not only deepen the understanding of the working principle of the single-cantilever GaN devices but also provide important references for device performance optimization and new applications in visible light communication (VLC) technology.

Micro magnetic field sensor based on bifunctional diodes

Multiple-quantum well (MQW) diodes can be used as bifunctional diodes due to the emission-detection spectral overlap. When integrated with magnetic fluids (MFs) that have tunable refractive index, they can be designed as micro magnetic field sensors. The sapphire substrate of the MQW diode chip that consists of an MQW transmitter and receiver that is directly exposed to the MF, and the external magnetic field strength is used to change the refractive index at the boundary between the sapphire and the MF, thus modulating the reflected light and realizing external magnetic field sensing. Verified by experimental measurements, the micromagnetic field sensor has a detection range of 0.001-0.05 T, a sensitivity of 127.3 µA/T, and a resolution of 4.5×10−5 T, with excellent stability and repeatability. Additionally, the sensor demonstrates good velocity resolution under dynamic magnetic fields and can detect the direction of magnetic field motion, providing significant application value.

Vertically stacked quantum well diodes for multifunctional applications

Dual-functioning multiple quantum well (MQW) diodes can simultaneously transmit and receive information through visible light. Here, we report vertically stacked red, green, and blue (RGB) MQW diodes for light detection and display applications. Both blue and green MQW diodes are monolithically integrated with distributed Bragg reflector (DBR) filters to realize the separation of light. The versatile RGB MQW transmitter/receiver system not only creates full-color display but also effectively separates RGB light into various colors. These results open feasible routes to generate multifunctional device for the development of full-color display and light receiver.

Multilevel Simultaneous Lighting-Imaging System.

In a III-nitride multiple quantum well (MQW) diode biased with a forward voltage, electrons recombine with holes inside the MQW region to emit light; meanwhile, the MQW diode utilizes the photoelectric effect to sense light when higher-energy photons hit the device to displace electrons in the diode. Both the injected electrons and the liberated electrons are gathered inside the diode, thereby giving rise to a simultaneous emission-detection phenomenon. The 4 × 4 MQW diodes could translate optical signals into electrical ones for image construction in the wavelength range from 320 to 440 nm. This technology will change the role of MQW diode-based displays since it can simultaneously transmit and receive optical signals, which is of crucial importance to the accelerating trend of multifunctional, intelligent displays using MQW diode technology.

Reflection-type photoplethysmography pulse sensor based on an integrated optoelectronic chip with a ring structure.

Reflection-type photoplethysmography (PPG) pulse sensors are widely used in consumer markets to measure cardiovascular signals. Different from off-chip package solutions in which the light-emitting diode (LED) and photodetector (PD) are in separate chips, a GaN integrated optoelectronic chip with a novel ring structure is proposed to realize a PPG pulse sensor. The integrated optoelectronic chip consists of two multiple-quantum well (MQW) diodes. For higher sensitivities, the central and peripheral MQW diodes are suitable as the LED and PD, respectively. The results indicate that the integrated optoelectronic chip based on a blue LED epitaxial wafer is more suitable for the integrated PPG sensor based on device performance. Moreover, the amplitude of the PPG pulse signal collected from fingertips is higher than that from a wrist. The feasibility of the reflection-type PPG pulse sensor based on a GaN integrated optoelectronic chip is fully verified with the advantages of smaller sizes and lower costs.

AlInGaAs MQW Transceiver with Electro-optic Modulation Characteristics for Free-Space Optical Communication and Sensing.

Integrated transceivers with electro-optic modulation characteristics are valuable for free-space optical communications and sensing. We propose an AlInGaAs multiple quantum well (MQW) transceiver with electro-optic modulation characteristics over a broad spectral range. Two identical AlInGaAs MQW diodes on a single wafer are used to transmit and receive optical signals and provide obvious electro-optic modulation for broad-spectrum light. The photocurrent modulation ratio reaches 13.9 and 11.3 for white light and 1550 nm infrared light, respectively, with varying bias voltages. The transceiver can identify environmental changes and forward electrical signals with different frequencies in the form of superimposed optical signals.

AlInGaAs Multiple Quantum Well-Integrated Device with Multifunction Light Emission/Detection and Electro-Optic Modulation in the Near-Infrared Range.

A monolithic photonic chip with multifunctional light emission/detection and electro-optic modulation capabilities in the near-infrared range is proposed and realized on an InP-based wafer. Two identical AlInGaAs multiple quantum well (MQW) diodes operating independently as light emission/detection devices are fabricated using a two-step etching process on a single wafer and connected via a straight waveguide. The photocurrent induced in the MQW diode for the detection process is generated by the infrared light emitted by the MQW diode during the emission process and transmitted via the straight waveguide. The MQW diode has an electro-optic modulation characteristic, and its spectral responsivity exhibits a blueshift with an increasingly negative bias voltage under external infrared laser excitation. An on-chip communication test is conducted to study the potential applications of the proposed monolithic photonic chip for transmission of optical signals in the near-infrared range.

Tandem dual-functioning multiple-quantum-well diodes for a self-powered light source.

Nitride-based semiconductor materials inherently have the intriguing functionalities of emission and photodetection. In particular, InGaN/GaN multiple-quantum-well (MQW) diodes exhibit dual light-harvesting and light-emitting modes of operation. Here a multifunctional system is proposed to integrate MQW diodes within a single chip with enhanced functionalities toward diverse applications of the Internet of Things (IoT). When we shine light on the MQW diodes, the absorbed photons can produce electron-hole pairs to charge an external capacitor. The energy of the ambient light is converted into electrical energy, which in turn powers the same MQW diode for lighting. The electrical energy within the capacitor is finally converted into the energy of the emitted light. Therefore, InGaN/GaN MQW diodes can be made to harvest energy from ambient light sources for IoT applications from a self-powered light source to intelligent terminal charging system.

Transferrable monolithic multicomponent system for near-ultraviolet optoelectronics

A monolithic near-ultraviolet multicomponent system is implemented on a 0.8-mm-diameter suspended membrane by integrating a transmitter, waveguide, and receiver into a single chip. Two identical InGaN/Al0.10Ga0.90N multiple-quantum well (MQW) diodes are fabricated using the same process flow, which separately function as a transmitter and receiver. There is a spectral overlap between the emission and detection spectra of the MQW diodes. Therefore, the receiver can respond to changes in the emission of the transmitter. The multicomponent system is mechanically transferred from silicon, and the wire-bonded transmitter on glass experimentally demonstrates spatial light transmission at 200 Mbps using non-return-to-zero on–off keying modulation.

Simultaneous Light-Emitting Light-Detecting Functionality of InGaN/GaN Multiple Quantum Well Diodes

The InGaN/GaN multiple-quantum-well (MQW) diode has selectable functionalities with emission and detection in the visible region due to the MQW-based p-n junction structure, which is employed to achieve on-chip optocoupling. Here, we propose to fabricate a suspended InGaN/GaN MQW diode on an III-nitride-on-silicon platform by a combination of silicon removal and III-nitride backside etching. Spatial simultaneous light-emitting light-detecting functionality, in which the detected light comes from an external light source, is experimentally demonstrated, endowing the MQW diode with the capability of contributing to intelligent displays as well as full-duplex visible light communication. As a transmitter, the InGaN/GaN MQW diode demonstrates out-of-plane data transmission at 120 Mb/s using visible light.

On-chip optical interconnect using visible light

We propose and fabricate a monolithic optical interconnect on a GaN-on-silicon platform using a wafer-level technique. Because the InGaN/GaN multiple-quantum-well diodes (MQWDs) can achieve light emission and detection simultaneously, the emitter and collector sharing identical MQW structure are produced using the same process. Suspended waveguides interconnect the emitter with the collector to form in-plane light coupling. Monolithic optical interconnect chip integrates the emitter, waveguide, base, and collector into a multi-component system with a common base. Output states superposition and 1×2 in-plane light communication are experimentally demonstrated. The proposed monolithic optical interconnect opens a promising way toward the diverse applications from in-plane visible light communication to light-induced artificial synaptic devices, intelligent display, on-chip imaging, and optical sensing.

On-Chip Integration Operating Under the Extraordinary Light Detection Mode of an InGaN/GaN Diode

In this letter, we build an on-chip photonic integration system on a GaN-on-silicon platform. Using silicon removal and back wafer etching techniques, two suspended InGaN/GaN multiple-quantum-well diodes (MQWDs), which are connected by suspended waveguides, are fabricated as a transmitter and a receiver, respectively, in the on-chip photonic integration system. The 100- $\mu \text{m}$ -long, 2- $\mu \text{m}$ -high, and 3- $\mu \text{m}$ -wide suspended waveguides are adopted for light coupling and transmission between the transmitter and the receiver. When the transmitter emits light, the InGaN/GaN MQWD simultaneously exhibits an extraordinary light detection mechanism in which the light-induced electron-hole pairs are greatly increased and can be rapidly cancelled by the injection current. The on-chip photonic integration system experimentally demonstrates the significantly improved 3-dB bandwidth and data transport performances when the receiver operates under the simultaneous light emission and detection mode.

Saturation Behavior for a Comb-Like Light-Induced Synaptic Transistor

We propose and fabricate a comb-like light-induced synaptic transistor composed of two InGaN/GaN multiple-quantum-well diodes (MQWDs) with a common base. One InGaN/GaN MQWD is used as an emitter of light, and another InGaN/GaN MQWD is used as a collector. When a presynaptic voltage is applied to the emitter to generate light, the collector absorbs the emitted light and demonstrates an excitatory postsynaptic voltage (EPSV). Saturated EPSV behavior occurs at the collector when multiple pulse signals are continuously applied to the emitter. The saturated EPSV value is increased and the saturated pulse number is reduced as the amplitude of the applied pulse signal increases. Experimental results indicate that continuous stimuli with a high pulse intensity will greatly improve the memory effect during the learning process.

Membrane-type photonic integration of InGaN/GaN multiple-quantum-well diodes and waveguide

We report here a membrane-type integration of InGaN/GaN multiple-quantum-well diodes (MQWDs) with a waveguide to build a highly integrated photonic system to perform functionalities on a GaN-on-silicon platform. Suspended MQWDs can be used as either for light-emitting diode (LED) or photodiode. In the fabricated photonic system, part of the LED emission is coupled into a suspended waveguide, and the guided light laterally propagates along the waveguide and is finally sensed by the photodiode. The photonic system can detect the in-plane guided light and the external incident light simultaneously. Planar optical communication experimentally demonstrates that the proof-of-concept monolithic photonic integration system can achieve the in-plane visible light communication. This work paves the way towards novel active electro-optical sensing systems and planar optical communication in the visible range.

Simultaneous light emission and detection of InGaN/GaN multiple quantum well diodes for in-plane visible light communication

This paper presents the design, fabrication, and experimental characterization of monolithically integrated p-n junction InGaN/GaN multiple quantum well diodes (MQWDs) and suspended waveguides. Suspended MQWDs can be used as transmitters and receivers simultaneously, and suspended waveguides are used for light coupling to create an in-plane visible light communication system. Compared to the waveguide with separation trench, the calculated total light efficiency is increased from 18% to 22% for the continuous waveguide. The MQWDs are characterized by their typical current-voltage performance, and the pulse excitation measurements confirm that the InGaN/GaN MQWDs can achieve the light emission and photodetection at the same time. The photocurrent measurements indicate that the photocurrent is modulated by a bias voltage and that the photons are being supplied from another transmitter. An experimental demonstration is presented showing that the proposed device works well for in-plane full-duplex communication using visible light.

Light Induced Synaptic Transistor With Dual Operation Modes

We propose and fabricate a light induced transistor using a combination of two multiple-quantum-well diodes (MQWDs) with a common n-electrode as the base. Both silicon removal and back wafer etching are conducted to obtain a suspended device architecture. The InGaN/GaN MQWD detects light only when the bias voltage is below the turn-ON voltage and can simultaneously achieve light emission and detection when it turns ON. Therefore, the light induced transistor operates with two distinct light detection modes. The excitatory postsynaptic voltages (EPSVs) are distinct due to the different decay times. Paired-pulse facilitation is experimentally demonstrated to mimic the synaptic plasticity behavior. The EPSV amplitudes are dependent on the pulse interval and pulse number.

Quantum-enhanced uniformity of carrier injection into successive quantum wells of multi-quantum-well structures

In multiple quantum well (MQW) structures carrier injection into distant quantum wells (QWs) described in a semi-classical way seems to be less effective than to closer ones. This may considerably affect performance of such MQW devices. Therefore, in the present paper a quantum-mechanical phenomenon, which may play a significant role in making the distribution of particles confined in a multi-well potential uniform, is presented. The time needed to distribute uniformly the particle is compared with the radiative lifetime in typical MQW lasers. Obtained results suggest that the described quantum-enhanced effect is in many cases effective enough to neglect originally non-uniform carrier injection into successive QWs of such a structure. It makes theoretical analysis of recombination phenomena in standard MQW diode lasers considerably easier.

Comparative study of temperature‐dependent electroluminescence efficiency in blue and green (In,Ga)N multiple‐quantum‐well diodes

AbstractElectroluminescence (EL) efficiency is comparatively investigated in the c ‐plane blue and green multiple‐quantum‐well (MQW) diodes over a wide temperature range (20‐300 K) and as a function of injection current (0.01‐10 mA). One striking result of the external quantum efficiency ηex observed is that for the blue diode strong EL quenching can occur at temperatures below 100 K in agreement with the previous reports, while no significant EL collapse is seen below 100 K for the green MQW diode, especially at low injection currents. This means that the anomalous low temperature EL reduction observed for the blue (In,Ga)N MQW diode is not solely determined by temperature only but strongly modified by changing the In content in the active layers, suggesting mechanisms ruled by forward‐bias dependent weaker carrier capture for the shallow potential depth MQW rather than hole freeze‐out at deep Mg acceptors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electroluminescence of In0.53Ga0.47As/GaAs0.5Sb0.5 Type-II Multiple Quantum Well Light-Emitting Diodes Grown on (111)B InP by Molecular Beam Epitaxy

In0.53Ga0.47As/GaAs0.5Sb0.5 type-II multiple-quantum-well (MQW) light-emitting diodes were grown on (111)B InP substrates by molecular beam epitaxy. The peak wavelength of the electroluminescence (EL) was at 2.08 µm at 11 K and at 2.28 µm at 300 K. It was found that the EL intensity of the type-II MQW diode on (111)B substrates was about one order of magnitude stronger than that on (100) InP substrates, which can be explained by the improved crystal quality of the MQW diode on the (111)B InP substrate.

Electroluminescence of In 0.53Ga 0.47As/GaAs 0.5Sb 0.5 type II multiple quantum well diodes lattice-matched to InP

Electroluminescence (EL) of In 0.53Ga 0.47As/GaAs 0.5Sb 0.5 type II multiple quantum well (MQW) diodes lattice-matched to InP substrates grown by molecular beam epitaxy was studied. A type II emission was clearly observed at 2.4 μm at 300 K. Furthermore, the EL intensity of the type II MQW diodes was larger than that of the InGaAs double heterostructure (DH) diodes. Temperature and injection current dependences of the EL spectrum were also investigated.