Avalanche LED Research Articles

Avalanche leds based on nanostructured silicon for optical interconnections

The paper analyzes the parameters of silicon avalanche LEDs and their use for electron-optical signal transmission systems. The advantages of silicon avalanche LEDs are shown, among which high speed and compatibility with silicon technology should be highlighted. Experimental avalanche LEDs based on nanostructured silicon were fabricated and studied. The results of controlling the electroluminescence spectrum of avalanche LEDs due to the choice of production conditions to form nanostructured silicon are presented. It was found that the temperature of the substrate during the deposition of the surface nanocomposite aluminum + silicon film affected the size of the formed silicon nanoparticles determining the spectral characteristics of avalanche LEDs. This allows shifting the maximum of their emission spectrum to a shorter wavelength region of the visible range due to the forming of smaller silicon nanoparticles. The authors have developed an optical interconnection system consisting of avalanche LEDs based on nanostructured silicon and a microchannel silicon wafer used to transmit a light signal. The study of various operating modes of the developed optoelectronic system was performed and an increase in the efficiency of optocouple based on avalanche LEDs to 0.2% due to the pulsed operating mode was achieved. It is shown that the efficiency of the optocouple increases with LED current and it is the pulsed mode of its operation that is characterized by the maximum current, which is due to more efficient removal of Joule heat in the intervals between pulses, ensuring stable operation of the entire system. The results obtained open up new opportunities for the development of optical interconnections between silicon chips and silicon optoelectronics in general.

INFLUENCE OF ANODIC ALUMINA USED AS SEPARATING DIELECTRIC OF SILICON AVALANCHE LEDs ON DIODE CHARACTERISTICS

A study of the influence of the formation regimes of avalanche LEDs based on nanostructured silicon on the parameters of the formed devices, such as the light emission voltage and the stability of operation has been performed. These parameters are an important factor for the practical use of avalanche LEDs in the development of silicon photonics products, the progress of which is associated with the future of integrated electronics. For the first time, the technological operation of local through electrochemical anodizing of aluminum in various electrolytes for the formation of a separating dielectric of Schottky contacts is presented. The influence of the built-in electric charge in the separation dielectric of silicon avalanche LEDs on their current-voltage characteristics is studied. It was found that the built-in negative electric charge increases the breakdown voltage of the Schottky contact, which results in an increase of the light emission efficiency of the diode structures. An explanation of this effect is presented on the basis that the built-in negative electric charge inside the anode oxide also creates a space charge region in silicon, which helps to reduce the effect of the concentration of field lines at the edges of diode structures, performing the function of protecting the Schottky contact from edge effects as well as protective areas do. It has been established that the highest avalanche breakdown voltage is observed in diode structures with anodic oxide formed in an electrolyte based on an aqueous solution of phosphoric acid. An analysis of the characteristics of LEDs at different temperatures of silicon substrates showed an increase of breakdown voltage with increasing temperature, which is typical for avalanche breakdown during impact ionization. Stable light emission of the formed LEDs was demonstrated in a wide range of operating voltages (8–16 V). The use of silicon avalanche LEDs both as discrete devices and in integrated electronics in general has been discussed.

3D Silicon Photonic Structures Based on Avalanche LED with Interconnections through Optical Interposer

Design and manufacturing technology of 3D silicon photonic structures with optical interconnections through microchannel vias interposers were developed. Silicon chips placed over each other were separated by the silicon microchannel vias interposer served as a light waveguide. Light emitting diodes and photodiodes were formed at the inner surfaces of silicon chips from nanostructured silicon clusters embedded into alumina matrix. The developed structure is characterized by the current conversion efficiency of 0.1% and can operate in the GHz frequency range.

실리콘 애벌런치 LED의 설계요소에 대한 분석

반도체 소자의 축소로 인한 처리속도의 향상이 더욱 어려워지고 있다. 따라서 반도체 산업의 새로운 도약을 위해서 실리콘을 이용한 광전소자의 출현(Silicon photonics)이 더욱 절실해지고 있다. 제조의 간단성, 반복성, 안정성, 고속성, 일반실리콘 반도체 공정과의 병존성 등의 특성으로 인해 애벌런치 항복에 의한 발광 소자는 실리콘 발광소자의 구현에 유력한 후보 중의 하나이다. 애벌런치 발광현상에 대해 전기적, 광학적 측정을 하고, 간단한 모델링과 시뮬레이션을 통하여 발광부위의 형태, <TEX>$n^{+}-p$</TEX> 접합의 깊이, 불순물의 농도, 에피층의 높이 등의 설계요소가 발광특성에 미치는 영향을 분석하였다. 시뮬레이션의 결과와 실제의 계측 결과를 비교하여, 차이점을 야기하는 이유, 애벌런치 항복의 발광현상을 설명하였고, 개선방안을 제시하였다. It is becoming more difficult to improve the device operating speed by shrinking the size of semiconductor devices. Therefore, for a new leap forward in the semiconductor industry, the advent of silicon opto-electronic devices, i.e., silicon photonics is more desperate. Silicon Avalanche LED is one of the prospective candidates to realize the practical silicon opto-electronic devices due to its simplicity of fabrication, repeatability, stability, high speed operation, and compatibility with silicon IC processing. We conducted the measurement of the electrical characteristics and the observation of the light-emitting phenomena using optical microscopy. We analyzed the influence of the design elements such as the shape of the light-emitting area and the depth of the <TEX>$n^{+}-p^{+}$</TEX> junction with simple device modeling and simulation. We compared the results of simulation and the measurement and explained the discrepancy between the results of the simulation and the measurement, and the suggestions for the improvement were given.

Si-based emissive microdisplays

Standard silicon microelectronics technology is very attractive for use in microdisplays, because it is the shortest way to highest pixel densities and integration of matrix with column and row drivers into a common chip. Use of nanostructured silicon light-emitting diodes (Si LEDs) may completely solve the problem of low compatibility of display elements and silicon chip. At present time the most suitable kinds of Si LEDs are porous silicon avalanche LEDs. They have such advantages as long operation lifetime, continuous spectrum, low operation voltages and extremely sharp voltage–current characteristic, nanosecond response time and high operation current density. This paper considers the background, approaches and achievements in design of the silicon-based LEDs and high-resolution matrix displays.

Porous Silicon Avalanche LEDs and their Applications in Optoelectronics and Information Displays

The use of silicon based light emitting diodes may completely solve the problem of low compatibility of optoelectronics elements and silicon chip. At present time the most suitable kinds of Si-LEDs are monocrystal and porous silicon avalanche LEDs. They have advantages such as long operation lifetime (> 10000 hours), continuous spectrum, which allows to filter RGB colors, operation voltages (< 12 V), extremely sharp voltage-current characteristic, nanosecond response time, and high high operation current densities (up to 8000 A/cm in pulse mode). Rather low energy efficiency (< 1%) is not so significant for near to eyes (NTE) microdisplays. These advantages open a way to design a high performance and cost effective passive addressed microdisplays.

Two- and multi-terminal CMOS/BiCMOS Si LED’s

Silicon is an indirect bandgap material, but light emission is observed from reverse biased pn junctions. Even though the quantum efficiency is low, it may still be advantageous to use these devices in all-silicon optoelectronic integrated circuits (OICs). In this paper new research results with regard to low-voltage field emission BiCMOS and CMOS two- and multi-terminal Si LEDs are presented. The differences observed between avalanche and low-voltage field emission LED performance are presented. It is shown that the low-voltage devices exhibit a square-law light intensity vs. reverse current non-linearity at low-current levels, but a linear dependency at higher currents, compared to the linear behaviour of avalanche devices at all current levels. The detail spectral characteristics of the field emission devices are investigated, showing that in the non-linear region of operation, the shape of the emitted spectrum changes, with reduced short wavelength generation at lower current levels. Bipolar junction transistor (BJT) multi-terminal devices are also discussed, and the square-law behaviour of these devices is presented.

Two- and multi-terminal silicon light emitting devices in standard CMOS/BiCMOS IC technology

Although silicon is an indirect bandgap material, light emission from reverse biased pn junctions has been observed. Although the quantum efficiency is low, it will be very advantageous to utilise these devices in all-silicon optoelectronic integrated circuits (OIC's). In this paper a review of our large area display and fibre-optic devices is given, followed by new research results achieved at CEFIM with regard to low voltage two-terminal line source Si LED's. A discussion of the differences observed between avalanche and field emission LED performance is presented. The detail spectral characteristics of field emission devices, and the spectral modulation of the optical signal from field emission light emitting devices are investigated. The design and simulation of a CMOS two-colour detector is presented, to be used as a detector for spectrally modulated optical signals. Gate-controlled diode MOS-like and carrier injection BJT-like multi-terminal devices are reviewed, and it is particularly indicated that both spatial modulation of the light emitting pattern and light intensity modulation can be achieved with these devices. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)