Kaikai Xu

Current–voltage characteristics and increase in the quantum efficiency of three-terminal gate and avalanche-based silicon LEDs

In this paper, the emission of visible light by a monolithically integrated silicon p-n junction under reverse-bias is discussed. The modulation of light intensity is achieved using an insulated-gate terminal on the surface of the p-n junction. By varying the gate voltage, the breakdown voltage of the p-n junction will be adjustable so that the reverse current I(sub) flowing through the p-n junction at a fixed reverse-bias voltage is changed. It is observed that the light, which is emitted from the defects located at the p-n junction, depends closely on the reverse current I(sub). In regard to the phenomenon of electroluminescence, the relationship between the optical emission power and the reverse current I(sub) is linear. On the other hand, it is observed that both the quantum efficiency and the power conversion efficiency are able to have obvious enhancement, although the reverse-bias of the p-n junction is reduced and the corresponding reverse-current is much lower. Moreover, the successful fabrication on monolithic silicon light source on the bulk silicon by means of standard silicon complementary metal-oxide-semiconductor process technology is presented.

A novel way to improve the quantum efficiency of silicon light-emitting diode in a standard silicon complementary metal–oxide–semiconductor technology

Silicon diode at avalanche breakdown has visible light emission in the depletion region. It is believed that this optical radiation comes from the kinetic energy loss of carriers generated by impact ionization colliding with immobile charge centers in the avalanche region. A theoretical model is presented to show the correlation of the hot carrier effect with the related photonic emission in high field. Meanwhile, a PMOSFET-like silicon light source device fabricated completely in the standard silicon CMOS process technology is measured to demonstrate that avalanching current is linearly proportional to optical emission power whether this light source acts as a two-terminal device (i.e., diode, the “p+ Source/Drain to n-Substrate junction” with floating the gate) or acts as a three-terminal device (i.e., gate-diode, the “p+ Source/Drain to n-Substrate junction” in the course of varying the gate voltage). Such linearity implies that control of the increasing current is a significant way to enhance the quan...

Electro-Optical Modulation Processes in Si-PMOSFET LEDs Operating in the Avalanche Light Emission Mode

In this paper, the switching characteristics as associated with p + n gated MOSFET silicon LED are reviewed. By employing the insulated-gate terminal, which allows the adjustment of P+ source/drain to N-substrate junction breakdown voltage, it is demonstrated that the electro-optical modulation in the Si-PMOSFET device operates as gate-controlled diodes. The PMOSFET device can operate as a Si-diode LED or an Si gate-controlled diode LED. The main features of switching transitions of Si-diode LED and Si gate-controlled diode LED are characterized, and a model is developed to explain the modulation speed, which is then reviewed. The upper limit derived value for the expected maximum modulation of the device could be in the range of a few hundred GHz. According to the best of my knowledge, despite the low efficiency, the Si-PMOSFET light-emitting device will be a potentially key component for silicon photonic integrated circuits for future computing I/O applications.

A Three-Terminal Silicon-PMOSFET-Like Light-Emitting Device (LED) for Optical Intensity Modulation

A Si- p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET)-like LED has been developed for light emission modulation. In contrast to a two-terminal Si-diode LED modulated by current signal, a major advantage of this three-terminal Si-PMOSFET LED is that the optical intensity modulation can be controlled by gate voltage signal, a standard CMOSFET operation to ease both logic circuit implementation and light modulation. The gate applied voltage induces carrier concentration modulation at both channel and source/drain region under the gate, thus modulating electric-field distribution and its light emission. Fabricated in a standard CMOS process technology, this Si-PMOSFET LED ensures its potential on realizing silicon optoelectronic integration.

Design and Fabrication of a Monolithic Optoelectronic Integrated Si CMOS LED Based on Hot-Carrier Effect

New research results with regard to two- and three-terminal Si-LEDs realized in a silicon MOS-like device fabricated using the CMOS process technology are presented. Since in the reverse-biased p-n junction the light intensity increases with electric field near the depletion region, the detailed characteristics of the field emission devices are investigated showing that in diode, the field varies with the p-n junctions reverse bias, and in gate-controlled diode the field varies with the voltage of gate-terminal. Due to the impossibility of experimentally measuring the field, two-dimensional device simulator is implemented to model the field distribution in the device. Simulated results show that, for the MOS-like device, the field in the three-terminal gate-controlled diode is of one order of magnitude higher than that in the two-terminal diode. In conclusion, the three-terminal device has a much better optical emission than the two-terminal device, and the emission enhancement is attributed to the tunneling-assisted photon emission that can only be achieved in the three-terminal gate-controlled diode. Good agreement is achieved between simulation and experiment.

Higher Intensity SiAvLEDs in an RF Bipolar Process Through Carrier Energy and Carrier Momentum Engineering

Carrier energy and momentum engineering design concepts have been utilized to realize higher intensity, up to 200 nW.μm -2 in p+nn+ silicon avalanche-based LEDs in a silicon 0.35-μm RF bipolar process. The spectral range is from 600- to 850-nm wavelength region. Best performance are up to 600-nW vertical emission in a 3-μm square active area at 10 V and 1 mA (200 nW.um-2). The achieved emitted optical intensity is about 100 fold better as compared with other published work for nearest related devices. In particular, evidence has been obtained that light emission in silicon are strongly related to scattering mechanisms in a high density n+ dopant matrix of phosphorous atoms in silicon that has been exposed to successive thermal cycles, as well on the optimization of the carrier energy and momentum distributions during such interactions.

Light-emitting device with monolithic integration on bulk silicon in standard complementary metal oxide semiconductor technology

Abstract. A silicon light-emitting device is designed and realized in standard 3-μm complementary metal oxide semiconductor (CMOS) integrated circuitry. Accordingly, it can be integrated with its signal processing CMOS and BiCMOS circuits on the same chip, thus enabling the fabrication of much needed all-silicon monolithic optoelectronic systems operated by a single supply. The device emitted light in a broad, bell-shaped spectrum from 500 to 850 nm with characteristic peaks at 650 and 750 nm. Initial investigations indicate that the quantum efficiency is of the order of 10−8 and the electric-to-optical power conversion efficiency is of the order of 10−9. This silicon light-emitting device has obvious applications in the electro-optical interconnect.

On the Design and Optimization of Three-Terminal Light-Emitting Device in Silicon CMOS Technology

The fabrication and performance of a MOSFET-like silicon light source that is able to monolithically integrate with silicon photo-detector in standard 3-μm CMOS process technology is introduced. The relation between gate voltage Vg and the breakdown voltage BV of the p-n junction in the gate-controlled diode is simulated to show that the modulation of light intensity can be reasonably explained by the decrease in BV, since the reverse-bias of the junction is fixed and the relation between the reverse current flowing through the p-n junction and the light intensity is linear. Based on such linearity, the paper attempts to explain the physical mechanisms responsible for the light emission in Si as a function of hot-carrier distribution functions. In order to further investigate the optical properties, measurement of photon emission and reverse current in silicon gate-controlled diode in avalanche breakdown has been made using electrical and near-infrared microscopy.

Analysis of simulation of multiterminal electro-optic modulator based on p-n junction in reverse bias

Abstract. A study of a silicon metal oxide semiconductor (MOS)-type light-emitting device (LED) in which the p–n junction works under a reverse bias and the gate voltage is applied to modulate the electric field distribution from the p+ region through the n region. The use of gate voltage could result in the generation of a field-induced junction which leads to a decrease of the operating voltage of the LED compared to the two terminal p–n junction LED. The dynamics of the photonic emission in the structure and its related response time, and then a more detailed theoretical and simulation understanding of the photonic emission is achieved, which definitively demonstrates the capability of the device in which a reverse-bias region showing light modulation with multi-GHz bandwidth and gigabit-per-second data rate at near-infrared wavelength. Although the emitted optical power is weak, it is advantageous to utilize the device in all-silicon optoelectronic integrated circuits, especially for short-distance on-chip optical interconnects achieved by standard complementary MOS technology.

Increased Efficiency of Silicon Light-Emitting Device in Standard Si-CMOS Technology

Light emission has been observed from silicon devices in the reverse avalanche mode. Compared with Si-diode light-emitting device (LED) (a two-terminal device), Si-pMOSFET LED (a three-terminal device) in which the optical emission power emitted from the device is controlled by the insulated-gate terminals voltage Vg has been discussed. Being similar to Si-diode LED, Si-pMOSFET LED can also be monolithically integrated into optical-electro integrated circuit that is fully compatible with the silicon CMOS process technology. Light emission efficiency enhancement observed at lower electric driving power in the Si-pMOSFET LED is presented, and the reverse-biased junction configuration of the silicon LED emit light in a broad spectrum from 450 to 800 nm with characteristic peaks around ~650 nm.